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 $69.84   6.864%   $74.6338   $74.63   $74.65   $74.60  
  Purchase #2 $211.78   10.639%   $234.3113   $234.31   $234.30   $234.30  
  Purchase #3 $114.48   11.172%   $127.2697   $127.27   $127.25   $127.30  
  Purchase #4 $50.53   5.660%   $53.39   $53.39   $53.40   $53.40  
  Purchase #5 $238.35   5.601%   $251.7   $251.70   $251.70   $251.70  
  Purchase #6 $248.27   9.329%   $271.4311   $271.43   $271.45   $271.40  
  Purchase #7 $20.34   6.873%   $21.738   $21.74   $21.75   $21.70  
  7 purchase totals = $953.59       $1,034.4739   $1,034.47   $1,034.50   $1,034.40