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 $41.66   5.535%   $43.9659   $43.97   $43.95   $44.00  
  Purchase #2 $25.96   8.234%   $28.0975   $28.10   $28.10   $28.10  
  Purchase #3 $188.36   13.325%   $213.459   $213.46   $213.45   $213.50  
  Purchase #4 $246.88   5.465%   $260.372   $260.37   $260.35   $260.40  
  Purchase #5 $238.33   12.797%   $268.8291   $268.83   $268.85   $268.80  
  Purchase #6 $72.61   4.347%   $75.7664   $75.77   $75.75   $75.80  
  Purchase #7 $164.33   6.715%   $175.3648   $175.36   $175.35   $175.40  
  7 purchase totals = $978.13       $1,065.8547   $1,065.86   $1,065.80   $1,066.00