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 $63.47   5.596%   $67.0218   $67.02   $67.00   $67.00  
  Purchase #2 $128.28   11.171%   $142.6102   $142.61   $142.60   $142.60  
  Purchase #3 $171.42   7.259%   $183.8634   $183.86   $183.85   $183.90  
  Purchase #4 $114.64   3.290%   $118.4117   $118.41   $118.40   $118.40  
  Purchase #5 $70.29   7.499%   $75.561   $75.56   $75.55   $75.60  
  Purchase #6 $110.39   4.655%   $115.5287   $115.53   $115.55   $115.50  
  Purchase #7 $50.41   5.187%   $53.0248   $53.02   $53.00   $53.00  
  7 purchase totals = $708.90       $756.0216   $756.01   $755.95   $756.00