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 $58.64   5.118%   $61.6412   $61.64   $61.65   $61.60  
  Purchase #2 $91.65   6.386%   $97.5028   $97.50   $97.50   $97.50  
  Purchase #3 $158.33   5.115%   $166.4286   $166.43   $166.45   $166.40  
  Purchase #4 $97.98   7.846%   $105.6675   $105.67   $105.65   $105.70  
  Purchase #5 $146.45   11.374%   $163.1072   $163.11   $163.10   $163.10  
  Purchase #6 $61.39   10.360%   $67.75   $67.75   $67.75   $67.80  
  Purchase #7 $246.61   5.666%   $260.5829   $260.58   $260.60   $260.60  
  7 purchase totals = $861.05       $922.6802   $922.68   $922.70   $922.70