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 $146.60   12.532%   $164.9719   $164.97   $164.95   $165.00  
  Purchase #2 $67.75   7.235%   $72.6517   $72.65   $72.65   $72.70  
  Purchase #3 $217.66   7.442%   $233.8583   $233.86   $233.85   $233.90  
  Purchase #4 $207.75   11.616%   $231.8822   $231.88   $231.90   $231.90  
  Purchase #5 $140.85   10.205%   $155.2237   $155.22   $155.20   $155.20  
  Purchase #6 $112.43   6.438%   $119.6682   $119.67   $119.65   $119.70  
  Purchase #7 $208.54   11.568%   $232.6639   $232.66   $232.65   $232.70  
  7 purchase totals = $1,101.58       $1,210.9199   $1,210.91   $1,210.85   $1,211.10