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 $215.83   7.646%   $232.3324   $232.33   $232.35   $232.30  
  Purchase #2 $139.97   9.276%   $152.9536   $152.95   $152.95   $153.00  
  Purchase #3 $51.99   13.444%   $58.9795   $58.98   $59.00   $59.00  
  Purchase #4 $192.91   12.624%   $217.263   $217.26   $217.25   $217.30  
  Purchase #5 $112.34   4.120%   $116.9684   $116.97   $116.95   $117.00  
  Purchase #6 $81.91   13.696%   $93.1284   $93.13   $93.15   $93.10  
  Purchase #7 $180.48   6.501%   $192.213   $192.21   $192.20   $192.20  
  7 purchase totals = $975.43       $1,063.8383   $1,063.83   $1,063.85   $1,063.90