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 $115.40   9.571%   $126.4449   $126.44   $126.45   $126.40  
  Purchase #2 $170.75   6.207%   $181.3485   $181.35   $181.35   $181.30  
  Purchase #3 $166.40   5.196%   $175.0461   $175.05   $175.05   $175.00  
  Purchase #4 $91.72   6.428%   $97.6158   $97.62   $97.60   $97.60  
  Purchase #5 $25.39   12.350%   $28.5257   $28.53   $28.55   $28.50  
  Purchase #6 $242.90   7.291%   $260.6098   $260.61   $260.60   $260.60  
  Purchase #7 $211.48   6.764%   $225.7845   $225.78   $225.80   $225.80  
  7 purchase totals = $1,024.04       $1,095.3753   $1,095.38   $1,095.40   $1,095.20