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 $225.26   5.299%   $237.1965   $237.20   $237.20   $237.20  
  Purchase #2 $157.61   8.707%   $171.3331   $171.33   $171.35   $171.30  
  Purchase #3 $171.37   11.756%   $191.5163   $191.52   $191.50   $191.50  
  Purchase #4 $24.45   11.312%   $27.2158   $27.22   $27.20   $27.20  
  Purchase #5 $62.82   6.245%   $66.7431   $66.74   $66.75   $66.70  
  Purchase #6 $231.30   7.203%   $247.9605   $247.96   $247.95   $248.00  
  Purchase #7 $159.78   6.481%   $170.1353   $170.14   $170.15   $170.10  
  7 purchase totals = $1,032.59       $1,112.1006   $1,112.11   $1,112.10   $1,112.00