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	$48.93	6.439%	$52.0806	$52.08	$52.10	$52.10
Purchase #2	$67.32	3.271%	$69.522	$69.52	$69.50	$69.50
Purchase #3	$225.96	13.139%	$255.6489	$255.65	$255.65	$255.60
Purchase #4	$53.59	3.820%	$55.6371	$55.64	$55.65	$55.60
Purchase #5	$45.88	10.590%	$50.7387	$50.74	$50.75	$50.70
Purchase #6	$206.79	10.803%	$229.1295	$229.13	$229.15	$229.10
Purchase #7	$20.48	11.240%	$22.782	$22.78	$22.80	$22.80
7 purchase totals =	$668.95		$735.5388	$735.54	$735.60	$735.40