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	$155.66	6.560%	$165.8713	$165.87	$165.85	$165.90
Purchase #2	$207.47	6.547%	$221.0531	$221.05	$221.05	$221.10
Purchase #3	$108.81	7.270%	$116.7205	$116.72	$116.70	$116.70
Purchase #4	$173.69	10.501%	$191.9292	$191.93	$191.95	$191.90
Purchase #5	$103.64	3.867%	$107.6478	$107.65	$107.65	$107.60
Purchase #6	$169.30	8.839%	$184.2644	$184.26	$184.25	$184.30
Purchase #7	$115.43	7.146%	$123.6786	$123.68	$123.70	$123.70
7 purchase totals =	$1,034.00		$1,111.1649	$1,111.16	$1,111.15	$1,111.20