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 $42.36   10.775%   $46.9243   $46.92   $46.90   $46.90  
  Purchase #2 $249.44   8.137%   $269.7369   $269.74   $269.75   $269.70  
  Purchase #3 $89.55   9.394%   $97.9623   $97.96   $97.95   $98.00  
  Purchase #4 $229.68   13.550%   $260.8016   $260.80   $260.80   $260.80  
  Purchase #5 $209.41   6.613%   $223.2583   $223.26   $223.25   $223.30  
  Purchase #6 $17.26   6.541%   $18.389   $18.39   $18.40   $18.40  
  Purchase #7 $183.59   9.433%   $200.908   $200.91   $200.90   $200.90  
  7 purchase totals = $1,021.29       $1,117.9804   $1,117.98   $1,117.95   $1,118.00