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 $67.59   11.103%   $75.0945   $75.09   $75.10   $75.10  
  Purchase #2 $200.53   6.309%   $213.1814   $213.18   $213.20   $213.20  
  Purchase #3 $212.71   10.407%   $234.8467   $234.85   $234.85   $234.80  
  Purchase #4 $185.65   4.769%   $194.5036   $194.50   $194.50   $194.50  
  Purchase #5 $214.64   7.438%   $230.6049   $230.60   $230.60   $230.60  
  Purchase #6 $236.53   11.306%   $263.2721   $263.27   $263.25   $263.30  
  Purchase #7 $235.29   9.490%   $257.619   $257.62   $257.60   $257.60  
  7 purchase totals = $1,352.94       $1,469.1222   $1,469.11   $1,469.10   $1,469.10