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 $91.87   3.387%   $94.9816   $94.98   $95.00   $95.00  
  Purchase #2 $191.98   9.777%   $210.7499   $210.75   $210.75   $210.70  
  Purchase #3 $153.76   11.337%   $171.1918   $171.19   $171.20   $171.20  
  Purchase #4 $101.36   3.347%   $104.7525   $104.75   $104.75   $104.80  
  Purchase #5 $17.61   9.293%   $19.2465   $19.25   $19.25   $19.20  
  Purchase #6 $26.65   13.150%   $30.1545   $30.15   $30.15   $30.20  
  Purchase #7 $131.41   3.720%   $136.2985   $136.30   $136.30   $136.30  
  7 purchase totals = $714.64       $767.3753   $767.37   $767.40   $767.40