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 $148.54   8.132%   $160.6193   $160.62   $160.60   $160.60  
  Purchase #2 $21.59   11.111%   $23.9889   $23.99   $24.00   $24.00  
  Purchase #3 $119.63   5.649%   $126.3879   $126.39   $126.40   $126.40  
  Purchase #4 $115.93   8.148%   $125.376   $125.38   $125.40   $125.40  
  Purchase #5 $26.34   13.182%   $29.8121   $29.81   $29.80   $29.80  
  Purchase #6 $187.51   3.562%   $194.1891   $194.19   $194.20   $194.20  
  Purchase #7 $198.42   8.629%   $215.5417   $215.54   $215.55   $215.50  
  7 purchase totals = $817.96       $875.9150   $875.92   $875.95   $875.90