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 $167.29   3.463%   $173.0833   $173.08   $173.10   $173.10  
  Purchase #2 $216.92   8.594%   $235.5621   $235.56   $235.55   $235.60  
  Purchase #3 $13.34   7.697%   $14.3668   $14.37   $14.35   $14.40  
  Purchase #4 $205.99   6.305%   $218.9777   $218.98   $219.00   $219.00  
  Purchase #5 $151.55   12.113%   $169.9073   $169.91   $169.90   $169.90  
  Purchase #6 $69.73   9.306%   $76.2191   $76.22   $76.20   $76.20  
  Purchase #7 $61.42   10.181%   $67.6732   $67.67   $67.65   $67.70  
  7 purchase totals = $886.24       $955.7895   $955.79   $955.75   $955.90