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 $89.70   5.859%   $94.9555   $94.96   $94.95   $95.00  
  Purchase #2 $209.70   3.145%   $216.2951   $216.30   $216.30   $216.30  
  Purchase #3 $56.95   9.557%   $62.3927   $62.39   $62.40   $62.40  
  Purchase #4 $113.44   10.209%   $125.0211   $125.02   $125.00   $125.00  
  Purchase #5 $67.36   13.797%   $76.6537   $76.65   $76.65   $76.70  
  Purchase #6 $64.34   11.766%   $71.9102   $71.91   $71.90   $71.90  
  Purchase #7 $149.89   13.406%   $169.9843   $169.98   $170.00   $170.00  
  7 purchase totals = $751.38       $817.2126   $817.21   $817.20   $817.30