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 $194.66   3.779%   $202.0162   $202.02   $202.00   $202.00  
  Purchase #2 $60.61   9.531%   $66.3867   $66.39   $66.40   $66.40  
  Purchase #3 $8.37   5.582%   $8.8372   $8.84   $8.85   $8.80  
  Purchase #4 $197.71   3.791%   $205.2052   $205.21   $205.20   $205.20  
  Purchase #5 $65.36   4.125%   $68.0561   $68.06   $68.05   $68.10  
  Purchase #6 $231.60   3.203%   $239.0181   $239.02   $239.00   $239.00  
  Purchase #7 $233.63   12.207%   $262.1492   $262.15   $262.15   $262.10  
  7 purchase totals = $991.94       $1,051.6687   $1,051.69   $1,051.65   $1,051.60