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 $85.98   10.664%   $95.1489   $95.15   $95.15   $95.10  
  Purchase #2 $47.57   4.802%   $49.8543   $49.85   $49.85   $49.90  
  Purchase #3 $158.41   9.701%   $173.7774   $173.78   $173.80   $173.80  
  Purchase #4 $179.33   7.260%   $192.3494   $192.35   $192.35   $192.30  
  Purchase #5 $222.45   6.141%   $236.1107   $236.11   $236.10   $236.10  
  Purchase #6 $210.26   13.209%   $238.0332   $238.03   $238.05   $238.00  
  Purchase #7 $155.75   6.327%   $165.6043   $165.60   $165.60   $165.60  
  7 purchase totals = $1,059.75       $1,150.8782   $1,150.87   $1,150.90   $1,150.80