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	$142.53	6.744%	$152.1422	$152.14	$152.15	$152.10
Purchase #2	$128.66	6.180%	$136.6112	$136.61	$136.60	$136.60
Purchase #3	$91.73	13.710%	$104.3062	$104.31	$104.30	$104.30
Purchase #4	$54.56	11.795%	$60.9954	$61.00	$61.00	$61.00
Purchase #5	$55.89	10.479%	$61.7467	$61.75	$61.75	$61.70
Purchase #6	$22.43	4.798%	$23.5062	$23.51	$23.50	$23.50
Purchase #7	$31.91	7.686%	$34.3626	$34.36	$34.35	$34.40
7 purchase totals =	$527.71		$573.6705	$573.68	$573.65	$573.60