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 $187.41   9.760%   $205.7012   $205.70   $205.70   $205.70  
  Purchase #2 $33.79   8.289%   $36.5909   $36.59   $36.60   $36.60  
  Purchase #3 $112.84   12.213%   $126.6211   $126.62   $126.60   $126.60  
  Purchase #4 $191.65   9.353%   $209.575   $209.58   $209.60   $209.60  
  Purchase #5 $124.38   4.810%   $130.3627   $130.36   $130.35   $130.40  
  Purchase #6 $173.59   10.275%   $191.4264   $191.43   $191.45   $191.40  
  Purchase #7 $205.79   3.496%   $212.9844   $212.98   $213.00   $213.00  
  7 purchase totals = $1,029.45       $1,113.2617   $1,113.26   $1,113.30   $1,113.30