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 $88.26   6.535%   $94.0278   $94.03   $94.05   $94.00  
  Purchase #2 $194.80   10.662%   $215.5696   $215.57   $215.55   $215.60  
  Purchase #3 $160.50   5.222%   $168.8813   $168.88   $168.90   $168.90  
  Purchase #4 $54.92   9.679%   $60.2357   $60.24   $60.25   $60.20  
  Purchase #5 $151.36   6.304%   $160.9017   $160.90   $160.90   $160.90  
  Purchase #6 $226.39   11.325%   $252.0287   $252.03   $252.05   $252.00  
  Purchase #7 $106.92   4.289%   $111.5058   $111.51   $111.50   $111.50  
  7 purchase totals = $983.15       $1,063.1506   $1,063.16   $1,063.20   $1,063.10