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 $162.57   8.212%   $175.9202   $175.92   $175.90   $175.90  
  Purchase #2 $116.78   6.329%   $124.171   $124.17   $124.15   $124.20  
  Purchase #3 $208.35   4.447%   $217.6153   $217.62   $217.60   $217.60  
  Purchase #4 $156.37   6.733%   $166.8984   $166.90   $166.90   $166.90  
  Purchase #5 $62.33   11.734%   $69.6438   $69.64   $69.65   $69.60  
  Purchase #6 $102.34   3.530%   $105.9526   $105.95   $105.95   $106.00  
  Purchase #7 $24.29   6.868%   $25.9582   $25.96   $25.95   $26.00  
  7 purchase totals = $833.03       $886.1595   $886.16   $886.10   $886.20