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 $77.64   11.738%   $86.7534   $86.75   $86.75   $86.80  
  Purchase #2 $90.27   5.388%   $95.1337   $95.13   $95.15   $95.10  
  Purchase #3 $231.55   3.798%   $240.3443   $240.34   $240.35   $240.30  
  Purchase #4 $26.60   11.221%   $29.5848   $29.58   $29.60   $29.60  
  Purchase #5 $238.33   10.438%   $263.2069   $263.21   $263.20   $263.20  
  Purchase #6 $56.97   3.407%   $58.911   $58.91   $58.90   $58.90  
  Purchase #7 $166.86   7.390%   $179.191   $179.19   $179.20   $179.20  
  7 purchase totals = $888.22       $953.1251   $953.11   $953.15   $953.10