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	$92.33	13.613%	$104.8989	$104.90	$104.90	$104.90
Purchase #2	$219.45	10.399%	$242.2706	$242.27	$242.25	$242.30
Purchase #3	$230.90	10.255%	$254.5788	$254.58	$254.60	$254.60
Purchase #4	$98.83	11.628%	$110.322	$110.32	$110.30	$110.30
Purchase #5	$158.94	13.522%	$180.4319	$180.43	$180.45	$180.40
Purchase #6	$53.81	4.133%	$56.034	$56.03	$56.05	$56.00
Purchase #7	$93.90	6.105%	$99.6326	$99.63	$99.65	$99.60
7 purchase totals =	$948.16		$1,048.1688	$1,048.16	$1,048.20	$1,048.10