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 $91.43   7.230%   $98.0404   $98.04   $98.05   $98.00  
  Purchase #2 $187.33   10.342%   $206.7037   $206.70   $206.70   $206.70  
  Purchase #3 $75.38   5.753%   $79.7166   $79.72   $79.70   $79.70  
  Purchase #4 $242.43   6.131%   $257.2934   $257.29   $257.30   $257.30  
  Purchase #5 $191.33   4.606%   $200.1427   $200.14   $200.15   $200.10  
  Purchase #6 $233.66   12.821%   $263.6175   $263.62   $263.60   $263.60  
  Purchase #7 $85.82   3.630%   $88.9353   $88.94   $88.95   $88.90  
  7 purchase totals = $1,107.38       $1,194.4496   $1,194.45   $1,194.45   $1,194.30