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 $57.51   5.390%   $60.6098   $60.61   $60.60   $60.60  
  Purchase #2 $61.92   4.790%   $64.886   $64.89   $64.90   $64.90  
  Purchase #3 $86.26   7.114%   $92.3965   $92.40   $92.40   $92.40  
  Purchase #4 $195.90   10.465%   $216.4009   $216.40   $216.40   $216.40  
  Purchase #5 $147.40   9.813%   $161.8644   $161.86   $161.85   $161.90  
  Purchase #6 $187.62   3.796%   $194.7421   $194.74   $194.75   $194.70  
  Purchase #7 $152.84   3.380%   $158.006   $158.01   $158.00   $158.00  
  7 purchase totals = $889.45       $948.9057   $948.91   $948.90   $948.90