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 $44.66   4.354%   $46.6045   $46.60   $46.60   $46.60  
  Purchase #2 $63.62   12.123%   $71.3327   $71.33   $71.35   $71.30  
  Purchase #3 $215.28   6.695%   $229.693   $229.69   $229.70   $229.70  
  Purchase #4 $143.87   3.781%   $149.3097   $149.31   $149.30   $149.30  
  Purchase #5 $118.88   4.321%   $124.0168   $124.02   $124.00   $124.00  
  Purchase #6 $59.58   5.154%   $62.6508   $62.65   $62.65   $62.70  
  Purchase #7 $202.96   5.763%   $214.6566   $214.66   $214.65   $214.70  
  7 purchase totals = $848.85       $898.2641   $898.26   $898.25   $898.30