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 $124.54   5.123%   $130.9202   $130.92   $130.90   $130.90  
  Purchase #2 $215.25   5.611%   $227.3277   $227.33   $227.35   $227.30  
  Purchase #3 $152.27   4.385%   $158.947   $158.95   $158.95   $158.90  
  Purchase #4 $227.72   4.627%   $238.2566   $238.26   $238.25   $238.30  
  Purchase #5 $91.64   5.182%   $96.3888   $96.39   $96.40   $96.40  
  Purchase #6 $187.44   13.529%   $212.7988   $212.80   $212.80   $212.80  
  Purchase #7 $81.40   8.874%   $88.6234   $88.62   $88.60   $88.60  
  7 purchase totals = $1,080.26       $1,153.2625   $1,153.27   $1,153.25   $1,153.20