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 $191.94   9.208%   $209.6138   $209.61   $209.60   $209.60  
  Purchase #2 $101.47   9.287%   $110.8935   $110.89   $110.90   $110.90  
  Purchase #3 $188.26   12.174%   $211.1788   $211.18   $211.20   $211.20  
  Purchase #4 $110.40   3.449%   $114.2077   $114.21   $114.20   $114.20  
  Purchase #5 $166.43   5.140%   $174.9845   $174.98   $175.00   $175.00  
  Purchase #6 $152.68   13.300%   $172.9864   $172.99   $173.00   $173.00  
  Purchase #7 $240.58   6.593%   $256.4414   $256.44   $256.45   $256.40  
  7 purchase totals = $1,151.76       $1,250.3061   $1,250.30   $1,250.35   $1,250.30