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	$34.52	8.418%	$37.4259	$37.43	$37.45	$37.40
Purchase #2	$84.61	8.240%	$91.5819	$91.58	$91.60	$91.60
Purchase #3	$223.54	3.798%	$232.03	$232.03	$232.05	$232.00
Purchase #4	$249.73	10.359%	$275.5995	$275.60	$275.60	$275.60
Purchase #5	$57.41	7.570%	$61.7559	$61.76	$61.75	$61.80
Purchase #6	$173.51	6.722%	$185.1733	$185.17	$185.15	$185.20
Purchase #7	$145.97	6.661%	$155.6931	$155.69	$155.70	$155.70
7 purchase totals =	$969.29		$1,039.2596	$1,039.26	$1,039.30	$1,039.30