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 $43.53   10.662%   $48.1712   $48.17   $48.15   $48.20  
  Purchase #2 $194.87   13.331%   $220.8481   $220.85   $220.85   $220.80  
  Purchase #3 $223.68   4.351%   $233.4123   $233.41   $233.40   $233.40  
  Purchase #4 $198.61   8.237%   $214.9695   $214.97   $214.95   $215.00  
  Purchase #5 $112.89   11.816%   $126.2291   $126.23   $126.25   $126.20  
  Purchase #6 $239.50   6.779%   $255.7357   $255.74   $255.75   $255.70  
  Purchase #7 $12.78   9.127%   $13.9464   $13.95   $13.95   $13.90  
  7 purchase totals = $1,025.86       $1,113.3123   $1,113.32   $1,113.30   $1,113.20