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 $58.32   8.107%   $63.048   $63.05   $63.05   $63.00  
  Purchase #2 $189.62   3.273%   $195.8263   $195.83   $195.85   $195.80  
  Purchase #3 $239.47   13.871%   $272.6869   $272.69   $272.70   $272.70  
  Purchase #4 $190.78   5.402%   $201.0859   $201.09   $201.10   $201.10  
  Purchase #5 $192.30   7.644%   $206.9994   $207.00   $207.00   $207.00  
  Purchase #6 $24.96   5.513%   $26.336   $26.34   $26.35   $26.30  
  Purchase #7 $238.42   8.729%   $259.2317   $259.23   $259.25   $259.20  
  7 purchase totals = $1,133.87       $1,225.2142   $1,225.23   $1,225.30   $1,225.10