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	$145.67	4.292%	$151.9222	$151.92	$151.90	$151.90
Purchase #2	$173.33	13.401%	$196.558	$196.56	$196.55	$196.60
Purchase #3	$177.99	5.332%	$187.4804	$187.48	$187.50	$187.50
Purchase #4	$238.75	3.304%	$246.6383	$246.64	$246.65	$246.60
Purchase #5	$52.73	8.643%	$57.2875	$57.29	$57.30	$57.30
Purchase #6	$34.78	12.142%	$39.003	$39.00	$39.00	$39.00
Purchase #7	$193.56	5.146%	$203.5206	$203.52	$203.50	$203.50
7 purchase totals =	$1,016.81		$1,082.4100	$1,082.41	$1,082.40	$1,082.40