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 $87.53   5.846%   $92.647   $92.65   $92.65   $92.60  
  Purchase #2 $216.71   13.839%   $246.7005   $246.70   $246.70   $246.70  
  Purchase #3 $102.48   6.403%   $109.0418   $109.04   $109.05   $109.00  
  Purchase #4 $23.69   9.522%   $25.9458   $25.95   $25.95   $25.90  
  Purchase #5 $139.68   4.491%   $145.953   $145.95   $145.95   $146.00  
  Purchase #6 $213.38   10.837%   $236.504   $236.50   $236.50   $236.50  
  Purchase #7 $151.54   12.445%   $170.3992   $170.40   $170.40   $170.40  
  7 purchase totals = $935.01       $1,027.1913   $1,027.19   $1,027.20   $1,027.10