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	$153.41	3.258%	$158.4081	$158.41	$158.40	$158.40
Purchase #2	$51.27	7.588%	$55.1604	$55.16	$55.15	$55.20
Purchase #3	$137.50	12.454%	$154.6243	$154.62	$154.60	$154.60
Purchase #4	$17.71	4.321%	$18.4752	$18.48	$18.50	$18.50
Purchase #5	$31.31	10.849%	$34.7068	$34.71	$34.70	$34.70
Purchase #6	$54.66	3.442%	$56.5414	$56.54	$56.55	$56.50
Purchase #7	$221.57	3.795%	$229.9786	$229.98	$230.00	$230.00
7 purchase totals =	$667.43		$707.8948	$707.90	$707.90	$707.90