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	$219.60	10.148%	$241.885	$241.89	$241.90	$241.90
Purchase #2	$130.66	13.335%	$148.0835	$148.08	$148.10	$148.10
Purchase #3	$152.88	4.578%	$159.8788	$159.88	$159.90	$159.90
Purchase #4	$14.68	5.501%	$15.4875	$15.49	$15.50	$15.50
Purchase #5	$54.34	9.285%	$59.3855	$59.39	$59.40	$59.40
Purchase #6	$127.73	7.850%	$137.7568	$137.76	$137.75	$137.80
Purchase #7	$56.61	9.173%	$61.8028	$61.80	$61.80	$61.80
7 purchase totals =	$756.50		$824.2799	$824.29	$824.35	$824.40