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 $172.69   12.424%   $194.145   $194.15   $194.15   $194.10  
  Purchase #2 $76.91   9.809%   $84.4541   $84.45   $84.45   $84.50  
  Purchase #3 $153.42   3.733%   $159.1472   $159.15   $159.15   $159.10  
  Purchase #4 $45.76   6.321%   $48.6525   $48.65   $48.65   $48.70  
  Purchase #5 $239.55   9.206%   $261.603   $261.60   $261.60   $261.60  
  Purchase #6 $203.30   7.152%   $217.84   $217.84   $217.85   $217.80  
  Purchase #7 $130.61   12.765%   $147.2824   $147.28   $147.30   $147.30  
  7 purchase totals = $1,022.24       $1,113.1242   $1,113.12   $1,113.15   $1,113.10