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 $59.63   4.466%   $62.2931   $62.29   $62.30   $62.30  
  Purchase #2 $51.59   3.370%   $53.3286   $53.33   $53.35   $53.30  
  Purchase #3 $237.44   12.468%   $267.044   $267.04   $267.05   $267.00  
  Purchase #4 $37.45   5.279%   $39.427   $39.43   $39.45   $39.40  
  Purchase #5 $176.51   6.506%   $187.9937   $187.99   $188.00   $188.00  
  Purchase #6 $143.85   11.234%   $160.0101   $160.01   $160.00   $160.00  
  Purchase #7 $98.51   7.594%   $105.9908   $105.99   $106.00   $106.00  
  7 purchase totals = $804.98       $876.0873   $876.08   $876.15   $876.00