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 $60.82   10.605%   $67.27   $67.27   $67.25   $67.30  
  Purchase #2 $156.85   6.872%   $167.6287   $167.63   $167.65   $167.60  
  Purchase #3 $194.63   5.218%   $204.7858   $204.79   $204.80   $204.80  
  Purchase #4 $206.89   10.154%   $227.8976   $227.90   $227.90   $227.90  
  Purchase #5 $249.37   3.620%   $258.3972   $258.40   $258.40   $258.40  
  Purchase #6 $205.87   5.546%   $217.2876   $217.29   $217.30   $217.30  
  Purchase #7 $234.76   8.169%   $253.9375   $253.94   $253.95   $253.90  
  7 purchase totals = $1,309.19       $1,397.2044   $1,397.22   $1,397.25   $1,397.20