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	$163.77	5.477%	$172.7397	$172.74	$172.75	$172.70
Purchase #2	$241.41	11.808%	$269.9157	$269.92	$269.90	$269.90
Purchase #3	$161.50	5.425%	$170.2614	$170.26	$170.25	$170.30
Purchase #4	$184.28	3.167%	$190.1161	$190.12	$190.10	$190.10
Purchase #5	$36.33	11.462%	$40.4941	$40.49	$40.50	$40.50
Purchase #6	$244.27	3.120%	$251.8912	$251.89	$251.90	$251.90
Purchase #7	$45.65	6.545%	$48.6378	$48.64	$48.65	$48.60
7 purchase totals =	$1,077.21		$1,144.0560	$1,144.06	$1,144.05	$1,144.00