Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $216.86   6.224%   $230.3574   $230.36   $230.35   $230.40  
  Purchase #2 $119.27   6.376%   $126.8747   $126.87   $126.85   $126.90  
  Purchase #3 $210.47   3.827%   $218.5247   $218.52   $218.50   $218.50  
  Purchase #4 $205.87   7.457%   $221.2217   $221.22   $221.20   $221.20  
  Purchase #5 $162.61   5.651%   $171.7991   $171.80   $171.80   $171.80  
  Purchase #6 $204.58   10.664%   $226.3964   $226.40   $226.40   $226.40  
  Purchase #7 $239.75   13.531%   $272.1906   $272.19   $272.20   $272.20  
  7 purchase totals = $1,359.41       $1,467.3646   $1,467.36   $1,467.30   $1,467.40