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 $93.97   7.318%   $100.8467   $100.85   $100.85   $100.80  
  Purchase #2 $182.80   7.871%   $197.1882   $197.19   $197.20   $197.20  
  Purchase #3 $106.66   3.305%   $110.1851   $110.19   $110.20   $110.20  
  Purchase #4 $203.56   5.185%   $214.1146   $214.11   $214.10   $214.10  
  Purchase #5 $178.73   12.653%   $201.3447   $201.34   $201.35   $201.30  
  Purchase #6 $144.92   3.466%   $149.9429   $149.94   $149.95   $149.90  
  Purchase #7 $33.59   10.462%   $37.1042   $37.10   $37.10   $37.10  
  7 purchase totals = $944.23       $1,010.7264   $1,010.72   $1,010.75   $1,010.60