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 $85.69   10.857%   $94.9934   $94.99   $95.00   $95.00  
  Purchase #2 $88.51   4.251%   $92.2726   $92.27   $92.25   $92.30  
  Purchase #3 $44.74   3.134%   $46.1422   $46.14   $46.15   $46.10  
  Purchase #4 $72.47   3.837%   $75.2507   $75.25   $75.25   $75.30  
  Purchase #5 $247.93   7.209%   $265.8033   $265.80   $265.80   $265.80  
  Purchase #6 $22.64   7.735%   $24.3912   $24.39   $24.40   $24.40  
  Purchase #7 $146.34   3.729%   $151.797   $151.80   $151.80   $151.80  
  7 purchase totals = $708.32       $750.6504   $750.64   $750.65   $750.70