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	$127.63	4.526%	$133.4065	$133.41	$133.40	$133.40
Purchase #2	$144.67	5.800%	$153.0609	$153.06	$153.05	$153.10
Purchase #3	$89.53	12.622%	$100.8305	$100.83	$100.85	$100.80
Purchase #4	$47.61	12.594%	$53.606	$53.61	$53.60	$53.60
Purchase #5	$108.66	10.355%	$119.9117	$119.91	$119.90	$119.90
Purchase #6	$132.56	12.794%	$149.5197	$149.52	$149.50	$149.50
Purchase #7	$181.43	12.748%	$204.5587	$204.56	$204.55	$204.60
7 purchase totals =	$832.09		$914.8940	$914.90	$914.85	$914.90