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 $95.58   10.178%   $105.3081   $105.31   $105.30   $105.30  
  Purchase #2 $33.43   4.137%   $34.813   $34.81   $34.80   $34.80  
  Purchase #3 $81.27   9.432%   $88.9354   $88.94   $88.95   $88.90  
  Purchase #4 $244.25   9.698%   $267.9374   $267.94   $267.95   $267.90  
  Purchase #5 $150.80   5.308%   $158.8045   $158.80   $158.80   $158.80  
  Purchase #6 $233.30   9.459%   $255.3678   $255.37   $255.35   $255.40  
  Purchase #7 $176.99   10.636%   $195.8147   $195.81   $195.80   $195.80  
  7 purchase totals = $1,015.62       $1,106.9809   $1,106.98   $1,106.95   $1,106.90