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 $188.48   3.431%   $194.9467   $194.95   $194.95   $194.90  
  Purchase #2 $35.73   7.322%   $38.3462   $38.35   $38.35   $38.30  
  Purchase #3 $110.64   5.547%   $116.7772   $116.78   $116.80   $116.80  
  Purchase #4 $152.70   3.628%   $158.24   $158.24   $158.25   $158.20  
  Purchase #5 $79.91   11.187%   $88.8495   $88.85   $88.85   $88.80  
  Purchase #6 $141.83   9.260%   $154.9635   $154.96   $154.95   $155.00  
  Purchase #7 $132.55   6.452%   $141.1021   $141.10   $141.10   $141.10  
  7 purchase totals = $841.84       $893.2252   $893.23   $893.25   $893.10