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 $40.92   13.307%   $46.3652   $46.37   $46.35   $46.40  
  Purchase #2 $228.72   8.319%   $247.7472   $247.75   $247.75   $247.70  
  Purchase #3 $21.96   12.749%   $24.7597   $24.76   $24.75   $24.80  
  Purchase #4 $194.62   6.628%   $207.5194   $207.52   $207.50   $207.50  
  Purchase #5 $124.77   6.607%   $133.0136   $133.01   $133.00   $133.00  
  Purchase #6 $187.68   12.108%   $210.4043   $210.40   $210.40   $210.40  
  Purchase #7 $133.34   9.610%   $146.154   $146.15   $146.15   $146.20  
  7 purchase totals = $932.01       $1,015.9634   $1,015.96   $1,015.90   $1,016.00