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 $24.70   8.738%   $26.8583   $26.86   $26.85   $26.90  
  Purchase #2 $244.77   12.755%   $275.9904   $275.99   $276.00   $276.00  
  Purchase #3 $189.84   12.690%   $213.9307   $213.93   $213.95   $213.90  
  Purchase #4 $49.97   11.310%   $55.6216   $55.62   $55.60   $55.60  
  Purchase #5 $185.43   8.471%   $201.1378   $201.14   $201.15   $201.10  
  Purchase #6 $102.95   3.508%   $106.5615   $106.56   $106.55   $106.60  
  Purchase #7 $204.36   5.542%   $215.6856   $215.69   $215.70   $215.70  
  7 purchase totals = $1,002.02       $1,095.7859   $1,095.79   $1,095.80   $1,095.80