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 $51.95   7.274%   $55.7288   $55.73   $55.75   $55.70  
  Purchase #2 $228.84   5.362%   $241.1104   $241.11   $241.10   $241.10  
  Purchase #3 $136.88   10.816%   $151.6849   $151.68   $151.70   $151.70  
  Purchase #4 $85.66   6.130%   $90.911   $90.91   $90.90   $90.90  
  Purchase #5 $162.38   6.147%   $172.3615   $172.36   $172.35   $172.40  
  Purchase #6 $229.66   9.768%   $252.0932   $252.09   $252.10   $252.10  
  Purchase #7 $62.89   8.572%   $68.2809   $68.28   $68.30   $68.30  
  7 purchase totals = $958.26       $1,032.1707   $1,032.16   $1,032.20   $1,032.20