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 $42.59   5.149%   $44.783   $44.78   $44.80   $44.80  
  Purchase #2 $67.42   13.622%   $76.604   $76.60   $76.60   $76.60  
  Purchase #3 $181.84   13.494%   $206.3775   $206.38   $206.40   $206.40  
  Purchase #4 $143.75   11.120%   $159.735   $159.74   $159.75   $159.70  
  Purchase #5 $151.78   13.763%   $172.6695   $172.67   $172.65   $172.70  
  Purchase #6 $192.73   6.230%   $204.7371   $204.74   $204.75   $204.70  
  Purchase #7 $186.96   9.381%   $204.4987   $204.50   $204.50   $204.50  
  7 purchase totals = $967.07       $1,069.4048   $1,069.41   $1,069.45   $1,069.40