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	$223.64	13.848%	$254.6097	$254.61	$254.60	$254.60
Purchase #2	$175.42	6.771%	$187.2977	$187.30	$187.30	$187.30
Purchase #3	$129.70	12.609%	$146.0539	$146.05	$146.05	$146.10
Purchase #4	$47.87	6.223%	$50.849	$50.85	$50.85	$50.80
Purchase #5	$82.73	12.481%	$93.0555	$93.06	$93.05	$93.10
Purchase #6	$123.25	11.855%	$137.8613	$137.86	$137.85	$137.90
Purchase #7	$144.97	3.197%	$149.6047	$149.60	$149.60	$149.60
7 purchase totals =	$927.58		$1,019.3318	$1,019.33	$1,019.30	$1,019.40