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 $84.65   4.692%   $88.6218   $88.62   $88.60   $88.60  
  Purchase #2 $184.46   6.352%   $196.1769   $196.18   $196.20   $196.20  
  Purchase #3 $66.30   7.173%   $71.0557   $71.06   $71.05   $71.10  
  Purchase #4 $216.58   5.800%   $229.1416   $229.14   $229.15   $229.10  
  Purchase #5 $35.78   5.455%   $37.7318   $37.73   $37.75   $37.70  
  Purchase #6 $219.95   8.117%   $237.8033   $237.80   $237.80   $237.80  
  Purchase #7 $11.31   3.501%   $11.706   $11.71   $11.70   $11.70  
  7 purchase totals = $819.03       $872.2371   $872.24   $872.25   $872.20