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	$11.54	5.826%	$12.2123	$12.21	$12.20	$12.20
Purchase #2	$21.29	5.106%	$22.3771	$22.38	$22.40	$22.40
Purchase #3	$101.27	5.422%	$106.7609	$106.76	$106.75	$106.80
Purchase #4	$153.33	6.162%	$162.7782	$162.78	$162.80	$162.80
Purchase #5	$178.69	12.165%	$200.4276	$200.43	$200.45	$200.40
Purchase #6	$145.40	10.377%	$160.4882	$160.49	$160.50	$160.50
Purchase #7	$78.78	13.681%	$89.5579	$89.56	$89.55	$89.60
7 purchase totals =	$690.30		$754.6022	$754.61	$754.65	$754.70