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 $227.49   7.812%   $245.2615   $245.26   $245.25   $245.30  
  Purchase #2 $88.25   4.655%   $92.358   $92.36   $92.35   $92.40  
  Purchase #3 $173.93   6.761%   $185.6894   $185.69   $185.70   $185.70  
  Purchase #4 $244.36   5.214%   $257.1009   $257.10   $257.10   $257.10  
  Purchase #5 $116.89   7.417%   $125.5597   $125.56   $125.55   $125.60  
  Purchase #6 $189.38   11.804%   $211.7344   $211.73   $211.75   $211.70  
  Purchase #7 $61.79   3.199%   $63.7667   $63.77   $63.75   $63.80  
  7 purchase totals = $1,102.09       $1,181.4706   $1,181.47   $1,181.45   $1,181.60