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 $116.62   7.216%   $125.0353   $125.04   $125.05   $125.00  
  Purchase #2 $159.38   10.369%   $175.9061   $175.91   $175.90   $175.90  
  Purchase #3 $28.37   5.494%   $29.9286   $29.93   $29.95   $29.90  
  Purchase #4 $178.35   8.597%   $193.6827   $193.68   $193.70   $193.70  
  Purchase #5 $107.98   8.360%   $117.0071   $117.01   $117.00   $117.00  
  Purchase #6 $99.32   8.493%   $107.7552   $107.76   $107.75   $107.80  
  Purchase #7 $89.42   9.531%   $97.9426   $97.94   $97.95   $97.90  
  7 purchase totals = $779.44       $847.2576   $847.27   $847.30   $847.20