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 $112.88   4.733%   $118.2226   $118.22   $118.20   $118.20  
  Purchase #2 $215.51   13.639%   $244.9034   $244.90   $244.90   $244.90  
  Purchase #3 $237.77   4.596%   $248.6979   $248.70   $248.70   $248.70  
  Purchase #4 $202.77   9.410%   $221.8507   $221.85   $221.85   $221.90  
  Purchase #5 $45.56   8.703%   $49.5251   $49.53   $49.55   $49.50  
  Purchase #6 $155.97   11.366%   $173.6976   $173.70   $173.70   $173.70  
  Purchase #7 $60.94   10.785%   $67.5124   $67.51   $67.50   $67.50  
  7 purchase totals = $1,031.40       $1,124.4097   $1,124.41   $1,124.40   $1,124.40