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 $204.51   4.152%   $213.0013   $213.00   $213.00   $213.00  
  Purchase #2 $215.43   10.685%   $238.4487   $238.45   $238.45   $238.40  
  Purchase #3 $225.46   8.588%   $244.8225   $244.82   $244.80   $244.80  
  Purchase #4 $100.69   12.322%   $113.097   $113.10   $113.10   $113.10  
  Purchase #5 $32.93   5.206%   $34.6443   $34.64   $34.65   $34.60  
  Purchase #6 $151.83   4.412%   $158.5287   $158.53   $158.55   $158.50  
  Purchase #7 $185.62   11.780%   $207.486   $207.49   $207.50   $207.50  
  7 purchase totals = $1,116.47       $1,210.0285   $1,210.03   $1,210.05   $1,209.90