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 $194.71   3.563%   $201.6475   $201.65   $201.65   $201.60  
  Purchase #2 $243.75   11.735%   $272.3541   $272.35   $272.35   $272.40  
  Purchase #3 $121.75   6.245%   $129.3533   $129.35   $129.35   $129.40  
  Purchase #4 $73.54   13.496%   $83.465   $83.47   $83.45   $83.50  
  Purchase #5 $197.62   7.659%   $212.7557   $212.76   $212.75   $212.80  
  Purchase #6 $174.54   9.566%   $191.2365   $191.24   $191.25   $191.20  
  Purchase #7 $25.35   12.355%   $28.482   $28.48   $28.50   $28.50  
  7 purchase totals = $1,031.26       $1,119.2941   $1,119.30   $1,119.30   $1,119.40