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 $164.65   5.485%   $173.6811   $173.68   $173.70   $173.70  
  Purchase #2 $216.98   11.486%   $241.9023   $241.90   $241.90   $241.90  
  Purchase #3 $44.95   5.628%   $47.4798   $47.48   $47.50   $47.50  
  Purchase #4 $167.66   11.640%   $187.1756   $187.18   $187.20   $187.20  
  Purchase #5 $212.89   13.347%   $241.3044   $241.30   $241.30   $241.30  
  Purchase #6 $197.29   13.341%   $223.6105   $223.61   $223.60   $223.60  
  Purchase #7 $138.73   7.498%   $149.132   $149.13   $149.15   $149.10  
  7 purchase totals = $1,143.15       $1,264.2857   $1,264.28   $1,264.35   $1,264.30