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	$144.31	7.665%	$155.3714	$155.37	$155.35	$155.40
Purchase #2	$19.60	11.858%	$21.9242	$21.92	$21.90	$21.90
Purchase #3	$75.63	10.339%	$83.4494	$83.45	$83.45	$83.40
Purchase #4	$124.40	9.504%	$136.223	$136.22	$136.20	$136.20
Purchase #5	$211.68	3.713%	$219.5397	$219.54	$219.55	$219.50
Purchase #6	$53.90	5.315%	$56.7648	$56.76	$56.75	$56.80
Purchase #7	$74.89	9.874%	$82.2846	$82.28	$82.30	$82.30
7 purchase totals =	$704.41		$755.5571	$755.54	$755.50	$755.50