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	$41.47	4.343%	$43.271	$43.27	$43.25	$43.30
Purchase #2	$213.56	8.120%	$230.9011	$230.90	$230.90	$230.90
Purchase #3	$155.99	13.664%	$177.3045	$177.30	$177.30	$177.30
Purchase #4	$54.82	5.255%	$57.7008	$57.70	$57.70	$57.70
Purchase #5	$174.31	9.215%	$190.3727	$190.37	$190.35	$190.40
Purchase #6	$93.67	6.248%	$99.5225	$99.52	$99.50	$99.50
Purchase #7	$246.65	11.552%	$275.143	$275.14	$275.15	$275.10
7 purchase totals =	$980.47		$1,074.2156	$1,074.20	$1,074.15	$1,074.20