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 $50.85   7.700%   $54.7655   $54.77   $54.75   $54.80  
  Purchase #2 $187.31   10.871%   $207.6725   $207.67   $207.65   $207.70  
  Purchase #3 $52.98   12.694%   $59.7053   $59.71   $59.70   $59.70  
  Purchase #4 $109.40   6.738%   $116.7714   $116.77   $116.75   $116.80  
  Purchase #5 $153.62   3.107%   $158.393   $158.39   $158.40   $158.40  
  Purchase #6 $229.70   7.868%   $247.7728   $247.77   $247.75   $247.80  
  Purchase #7 $240.37   4.628%   $251.4943   $251.49   $251.50   $251.50  
  7 purchase totals = $1,024.23       $1,096.5748   $1,096.57   $1,096.50   $1,096.70