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 $113.97   11.130%   $126.6549   $126.65   $126.65   $126.70  
  Purchase #2 $160.29   8.825%   $174.4356   $174.44   $174.45   $174.40  
  Purchase #3 $62.98   6.325%   $66.9635   $66.96   $66.95   $67.00  
  Purchase #4 $56.95   8.687%   $61.8972   $61.90   $61.90   $61.90  
  Purchase #5 $33.72   6.160%   $35.7972   $35.80   $35.80   $35.80  
  Purchase #6 $148.81   3.736%   $154.3695   $154.37   $154.35   $154.40  
  Purchase #7 $140.93   4.335%   $147.0393   $147.04   $147.05   $147.00  
  7 purchase totals = $717.65       $767.1572   $767.16   $767.15   $767.20