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 $196.26   3.192%   $202.5246   $202.52   $202.50   $202.50  
  Purchase #2 $118.98   12.350%   $133.674   $133.67   $133.65   $133.70  
  Purchase #3 $20.50   11.478%   $22.853   $22.85   $22.85   $22.90  
  Purchase #4 $240.93   4.853%   $252.6223   $252.62   $252.60   $252.60  
  Purchase #5 $132.45   11.145%   $147.2116   $147.21   $147.20   $147.20  
  Purchase #6 $245.92   4.473%   $256.92   $256.92   $256.90   $256.90  
  Purchase #7 $61.63   13.845%   $70.1627   $70.16   $70.15   $70.20  
  7 purchase totals = $1,016.67       $1,085.9682   $1,085.95   $1,085.85   $1,086.00