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 $174.96   11.829%   $195.656   $195.66   $195.65   $195.70  
  Purchase #2 $162.74   12.123%   $182.469   $182.47   $182.45   $182.50  
  Purchase #3 $165.28   5.149%   $173.7903   $173.79   $173.80   $173.80  
  Purchase #4 $217.71   13.329%   $246.7286   $246.73   $246.75   $246.70  
  Purchase #5 $167.85   10.413%   $185.3282   $185.33   $185.35   $185.30  
  Purchase #6 $192.85   6.483%   $205.3525   $205.35   $205.35   $205.40  
  Purchase #7 $23.91   7.179%   $25.6265   $25.63   $25.65   $25.60  
  7 purchase totals = $1,105.30       $1,214.9511   $1,214.96   $1,215.00   $1,215.00