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	$146.88	3.865%	$152.5569	$152.56	$152.55	$152.60
Purchase #2	$66.43	6.254%	$70.5845	$70.58	$70.60	$70.60
Purchase #3	$238.65	11.655%	$266.4647	$266.46	$266.45	$266.50
Purchase #4	$173.46	13.438%	$196.7696	$196.77	$196.75	$196.80
Purchase #5	$42.86	6.169%	$45.504	$45.50	$45.50	$45.50
Purchase #6	$32.41	3.212%	$33.451	$33.45	$33.45	$33.50
Purchase #7	$60.31	7.738%	$64.9768	$64.98	$65.00	$65.00
7 purchase totals =	$761.00		$830.3075	$830.30	$830.30	$830.50