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 $118.52   6.558%   $126.2925   $126.29   $126.30   $126.30  
  Purchase #2 $106.52   3.568%   $110.3206   $110.32   $110.30   $110.30  
  Purchase #3 $40.82   12.625%   $45.9735   $45.97   $45.95   $46.00  
  Purchase #4 $61.45   11.738%   $68.663   $68.66   $68.65   $68.70  
  Purchase #5 $179.37   8.617%   $194.8263   $194.83   $194.85   $194.80  
  Purchase #6 $134.95   5.177%   $141.9364   $141.94   $141.95   $141.90  
  Purchase #7 $56.89   12.691%   $64.1099   $64.11   $64.10   $64.10  
  7 purchase totals = $698.52       $752.1222   $752.12   $752.10   $752.10