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	$92.87	13.821%	$105.7056	$105.71	$105.70	$105.70
Purchase #2	$92.72	4.226%	$96.6383	$96.64	$96.65	$96.60
Purchase #3	$162.82	6.136%	$172.8106	$172.81	$172.80	$172.80
Purchase #4	$10.79	13.213%	$12.2157	$12.22	$12.20	$12.20
Purchase #5	$32.32	8.748%	$35.1474	$35.15	$35.15	$35.10
Purchase #6	$6.73	8.657%	$7.3126	$7.31	$7.30	$7.30
Purchase #7	$31.32	3.866%	$32.5308	$32.53	$32.55	$32.50
7 purchase totals =	$429.57		$462.3610	$462.37	$462.35	$462.20