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 $53.61   13.699%   $60.954   $60.95   $60.95   $61.00  
  Purchase #2 $170.45   12.654%   $192.0187   $192.02   $192.00   $192.00  
  Purchase #3 $11.78   9.490%   $12.8979   $12.90   $12.90   $12.90  
  Purchase #4 $91.43   3.549%   $94.6749   $94.67   $94.65   $94.70  
  Purchase #5 $201.66   13.412%   $228.7066   $228.71   $228.70   $228.70  
  Purchase #6 $209.77   11.742%   $234.4012   $234.40   $234.40   $234.40  
  Purchase #7 $117.42   6.714%   $125.3036   $125.30   $125.30   $125.30  
  7 purchase totals = $856.12       $948.9569   $948.95   $948.90   $949.00