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 $39.42   10.647%   $43.617   $43.62   $43.60   $43.60  
  Purchase #2 $226.43   3.509%   $234.3754   $234.38   $234.40   $234.40  
  Purchase #3 $93.96   4.667%   $98.3451   $98.35   $98.35   $98.30  
  Purchase #4 $14.71   5.534%   $15.5241   $15.52   $15.50   $15.50  
  Purchase #5 $235.73   5.480%   $248.648   $248.65   $248.65   $248.60  
  Purchase #6 $83.59   5.631%   $88.297   $88.30   $88.30   $88.30  
  Purchase #7 $141.54   8.454%   $153.5058   $153.51   $153.50   $153.50  
  7 purchase totals = $835.38       $882.3124   $882.33   $882.30   $882.20