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 $64.37   4.548%   $67.2975   $67.30   $67.30   $67.30  
  Purchase #2 $214.30   10.151%   $236.0536   $236.05   $236.05   $236.10  
  Purchase #3 $206.96   6.569%   $220.5552   $220.56   $220.55   $220.60  
  Purchase #4 $95.38   11.601%   $106.445   $106.45   $106.45   $106.40  
  Purchase #5 $245.88   10.671%   $272.1179   $272.12   $272.10   $272.10  
  Purchase #6 $213.76   8.583%   $232.107   $232.11   $232.10   $232.10  
  Purchase #7 $51.46   11.505%   $57.3805   $57.38   $57.40   $57.40  
  7 purchase totals = $1,092.11       $1,191.9567   $1,191.97   $1,191.95   $1,192.00