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 $93.75   10.181%   $103.2947   $103.29   $103.30   $103.30  
  Purchase #2 $171.82   13.490%   $194.9985   $195.00   $195.00   $195.00  
  Purchase #3 $136.77   7.248%   $146.6831   $146.68   $146.70   $146.70  
  Purchase #4 $9.32   3.289%   $9.6265   $9.63   $9.65   $9.60  
  Purchase #5 $226.70   3.444%   $234.5075   $234.51   $234.50   $234.50  
  Purchase #6 $232.64   4.603%   $243.3484   $243.35   $243.35   $243.30  
  Purchase #7 $8.51   4.613%   $8.9026   $8.90   $8.90   $8.90  
  7 purchase totals = $879.51       $941.3613   $941.36   $941.40   $941.30