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 $86.31   10.244%   $95.1516   $95.15   $95.15   $95.20  
  Purchase #2 $212.55   11.817%   $237.667   $237.67   $237.65   $237.70  
  Purchase #3 $203.26   12.760%   $229.196   $229.20   $229.20   $229.20  
  Purchase #4 $148.27   8.761%   $161.2599   $161.26   $161.25   $161.30  
  Purchase #5 $29.27   3.162%   $30.1955   $30.20   $30.20   $30.20  
  Purchase #6 $174.76   11.112%   $194.1793   $194.18   $194.20   $194.20  
  Purchase #7 $85.71   11.238%   $95.3421   $95.34   $95.35   $95.30  
  7 purchase totals = $940.13       $1,042.9914   $1,043.00   $1,043.00   $1,043.10