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 $89.63   6.316%   $95.291   $95.29   $95.30   $95.30  
  Purchase #2 $47.43   6.530%   $50.5272   $50.53   $50.55   $50.50  
  Purchase #3 $171.83   12.386%   $193.1129   $193.11   $193.10   $193.10  
  Purchase #4 $127.75   4.413%   $133.3876   $133.39   $133.40   $133.40  
  Purchase #5 $225.73   7.679%   $243.0638   $243.06   $243.05   $243.10  
  Purchase #6 $221.74   11.755%   $247.8055   $247.81   $247.80   $247.80  
  Purchase #7 $220.42   10.730%   $244.0711   $244.07   $244.05   $244.10  
  7 purchase totals = $1,104.53       $1,207.2591   $1,207.26   $1,207.25   $1,207.30