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 $232.52   10.205%   $256.2487   $256.25   $256.25   $256.20  
  Purchase #2 $235.62   11.408%   $262.4995   $262.50   $262.50   $262.50  
  Purchase #3 $44.54   11.645%   $49.7267   $49.73   $49.75   $49.70  
  Purchase #4 $107.57   9.798%   $118.1097   $118.11   $118.10   $118.10  
  Purchase #5 $212.59   6.758%   $226.9568   $226.96   $226.95   $227.00  
  Purchase #6 $221.73   3.577%   $229.6613   $229.66   $229.65   $229.70  
  Purchase #7 $201.56   7.761%   $217.2031   $217.20   $217.20   $217.20  
  7 purchase totals = $1,256.13       $1,360.4058   $1,360.41   $1,360.40   $1,360.40