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	$222.60	6.456%	$236.9711	$236.97	$236.95	$237.00
Purchase #2	$152.90	11.252%	$170.1043	$170.10	$170.10	$170.10
Purchase #3	$195.84	13.567%	$222.4096	$222.41	$222.40	$222.40
Purchase #4	$57.46	3.384%	$59.4044	$59.40	$59.40	$59.40
Purchase #5	$152.65	4.490%	$159.504	$159.50	$159.50	$159.50
Purchase #6	$70.30	9.585%	$77.0383	$77.04	$77.05	$77.00
Purchase #7	$241.91	10.136%	$266.43	$266.43	$266.45	$266.40
7 purchase totals =	$1,093.66		$1,191.8617	$1,191.85	$1,191.85	$1,191.80