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 $213.82   5.463%   $225.501   $225.50   $225.50   $225.50  
  Purchase #2 $22.27   7.677%   $23.9797   $23.98   $24.00   $24.00  
  Purchase #3 $238.36   5.191%   $250.7333   $250.73   $250.75   $250.70  
  Purchase #4 $220.61   7.182%   $236.4542   $236.45   $236.45   $236.50  
  Purchase #5 $77.57   9.826%   $85.192   $85.19   $85.20   $85.20  
  Purchase #6 $55.99   5.381%   $59.0028   $59.00   $59.00   $59.00  
  Purchase #7 $154.40   11.485%   $172.1328   $172.13   $172.15   $172.10  
  7 purchase totals = $983.02       $1,052.9958   $1,052.98   $1,053.05   $1,053.00