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 $62.61   9.770%   $68.727   $68.73   $68.75   $68.70  
  Purchase #2 $244.72   12.522%   $275.3638   $275.36   $275.35   $275.40  
  Purchase #3 $74.34   5.302%   $78.2815   $78.28   $78.30   $78.30  
  Purchase #4 $187.82   6.268%   $199.5926   $199.59   $199.60   $199.60  
  Purchase #5 $6.39   6.265%   $6.7903   $6.79   $6.80   $6.80  
  Purchase #6 $132.64   9.313%   $144.9928   $144.99   $145.00   $145.00  
  Purchase #7 $250.67   10.800%   $277.7424   $277.74   $277.75   $277.70  
  7 purchase totals = $959.19       $1,051.4904   $1,051.48   $1,051.55   $1,051.50