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 $57.49   8.759%   $62.5255   $62.53   $62.55   $62.50  
  Purchase #2 $167.28   10.408%   $184.6905   $184.69   $184.70   $184.70  
  Purchase #3 $48.62   6.386%   $51.7249   $51.72   $51.70   $51.70  
  Purchase #4 $93.51   8.777%   $101.7174   $101.72   $101.70   $101.70  
  Purchase #5 $179.92   13.142%   $203.5651   $203.57   $203.55   $203.60  
  Purchase #6 $41.32   4.539%   $43.1955   $43.20   $43.20   $43.20  
  Purchase #7 $133.93   8.412%   $145.1962   $145.20   $145.20   $145.20  
  7 purchase totals = $722.07       $792.6151   $792.63   $792.60   $792.60