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 $173.62   11.774%   $194.062   $194.06   $194.05   $194.10  
  Purchase #2 $106.40   10.860%   $117.955   $117.96   $117.95   $118.00  
  Purchase #3 $162.45   4.552%   $169.8447   $169.84   $169.85   $169.80  
  Purchase #4 $158.86   6.604%   $169.3511   $169.35   $169.35   $169.40  
  Purchase #5 $173.93   9.147%   $189.8394   $189.84   $189.85   $189.80  
  Purchase #6 $45.52   10.714%   $50.397   $50.40   $50.40   $50.40  
  Purchase #7 $62.50   9.278%   $68.2988   $68.30   $68.30   $68.30  
  7 purchase totals = $883.28       $959.7480   $959.75   $959.75   $959.80