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	$158.69	8.563%	$172.2786	$172.28	$172.30	$172.30
Purchase #2	$135.52	7.530%	$145.7247	$145.72	$145.70	$145.70
Purchase #3	$139.78	11.293%	$155.5654	$155.57	$155.55	$155.60
Purchase #4	$185.72	4.178%	$193.4794	$193.48	$193.50	$193.50
Purchase #5	$249.88	11.302%	$278.1214	$278.12	$278.10	$278.10
Purchase #6	$114.83	11.371%	$127.8873	$127.89	$127.90	$127.90
Purchase #7	$191.83	4.763%	$200.9669	$200.97	$200.95	$201.00
7 purchase totals =	$1,176.25		$1,274.0237	$1,274.03	$1,274.00	$1,274.10