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 $195.54   3.792%   $202.9549   $202.95   $202.95   $203.00  
  Purchase #2 $76.42   12.338%   $85.8487   $85.85   $85.85   $85.80  
  Purchase #3 $141.69   12.509%   $159.414   $159.41   $159.40   $159.40  
  Purchase #4 $216.28   6.308%   $229.9229   $229.92   $229.90   $229.90  
  Purchase #5 $205.42   7.464%   $220.7525   $220.75   $220.75   $220.80  
  Purchase #6 $151.42   3.769%   $157.127   $157.13   $157.15   $157.10  
  Purchase #7 $230.59   6.320%   $245.1633   $245.16   $245.15   $245.20  
  7 purchase totals = $1,217.36       $1,301.1833   $1,301.17   $1,301.15   $1,301.20