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 $71.37   6.463%   $75.9826   $75.98   $76.00   $76.00  
  Purchase #2 $230.63   12.821%   $260.1991   $260.20   $260.20   $260.20  
  Purchase #3 $64.56   3.649%   $66.9158   $66.92   $66.90   $66.90  
  Purchase #4 $153.91   11.223%   $171.1833   $171.18   $171.20   $171.20  
  Purchase #5 $53.61   8.799%   $58.3271   $58.33   $58.35   $58.30  
  Purchase #6 $155.42   13.257%   $176.024   $176.02   $176.00   $176.00  
  Purchase #7 $214.30   13.858%   $243.9977   $244.00   $244.00   $244.00  
  7 purchase totals = $943.80       $1,052.6296   $1,052.63   $1,052.65   $1,052.60