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 $86.36   11.373%   $96.1817   $96.18   $96.20   $96.20  
  Purchase #2 $243.34   8.132%   $263.1284   $263.13   $263.15   $263.10  
  Purchase #3 $241.43   13.865%   $274.9043   $274.90   $274.90   $274.90  
  Purchase #4 $28.97   7.352%   $31.0999   $31.10   $31.10   $31.10  
  Purchase #5 $143.38   12.553%   $161.3785   $161.38   $161.40   $161.40  
  Purchase #6 $179.53   8.639%   $195.0396   $195.04   $195.05   $195.00  
  Purchase #7 $223.32   7.852%   $240.8551   $240.86   $240.85   $240.90  
  7 purchase totals = $1,146.33       $1,262.5875   $1,262.59   $1,262.65   $1,262.60