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 $209.59   8.299%   $226.9839   $226.98   $227.00   $227.00  
  Purchase #2 $159.29   8.619%   $173.0192   $173.02   $173.00   $173.00  
  Purchase #3 $101.27   9.485%   $110.8755   $110.88   $110.90   $110.90  
  Purchase #4 $63.42   7.209%   $67.9919   $67.99   $68.00   $68.00  
  Purchase #5 $97.50   8.679%   $105.962   $105.96   $105.95   $106.00  
  Purchase #6 $213.57   5.804%   $225.9656   $225.97   $225.95   $226.00  
  Purchase #7 $109.74   11.142%   $121.9672   $121.97   $121.95   $122.00  
  7 purchase totals = $954.38       $1,032.7653   $1,032.77   $1,032.75   $1,032.90