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 $118.66   6.365%   $126.2127   $126.21   $126.20   $126.20  
  Purchase #2 $209.59   5.187%   $220.4614   $220.46   $220.45   $220.50  
  Purchase #3 $22.61   10.163%   $24.9079   $24.91   $24.90   $24.90  
  Purchase #4 $241.66   13.518%   $274.3276   $274.33   $274.35   $274.30  
  Purchase #5 $199.29   7.378%   $213.9936   $213.99   $214.00   $214.00  
  Purchase #6 $58.96   9.569%   $64.6019   $64.60   $64.60   $64.60  
  Purchase #7 $155.83   9.703%   $170.9502   $170.95   $170.95   $171.00  
  7 purchase totals = $1,006.60       $1,095.4553   $1,095.45   $1,095.45   $1,095.50