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	$124.38	4.374%	$129.8204	$129.82	$129.80	$129.80
Purchase #2	$109.80	13.400%	$124.5132	$124.51	$124.50	$124.50
Purchase #3	$158.53	10.657%	$175.4245	$175.42	$175.40	$175.40
Purchase #4	$108.48	8.406%	$117.5988	$117.60	$117.60	$117.60
Purchase #5	$179.34	6.637%	$191.2428	$191.24	$191.25	$191.20
Purchase #6	$161.92	7.501%	$174.0656	$174.07	$174.05	$174.10
Purchase #7	$226.73	12.866%	$255.9011	$255.90	$255.90	$255.90
7 purchase totals =	$1,069.18		$1,168.5664	$1,168.56	$1,168.50	$1,168.50