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	$250.66	12.158%	$281.1352	$281.14	$281.15	$281.10
Purchase #2	$130.54	5.798%	$138.1087	$138.11	$138.10	$138.10
Purchase #3	$179.82	11.102%	$199.7836	$199.78	$199.80	$199.80
Purchase #4	$151.90	4.295%	$158.4241	$158.42	$158.40	$158.40
Purchase #5	$129.28	4.570%	$135.1881	$135.19	$135.20	$135.20
Purchase #6	$101.66	7.690%	$109.4777	$109.48	$109.50	$109.50
Purchase #7	$56.90	5.335%	$59.9356	$59.94	$59.95	$59.90
7 purchase totals =	$1,000.76		$1,082.0530	$1,082.06	$1,082.10	$1,082.00