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	$6.93	10.279%	$7.6423	$7.64	$7.65	$7.60
Purchase #2	$57.81	11.707%	$64.5778	$64.58	$64.60	$64.60
Purchase #3	$89.99	4.644%	$94.1691	$94.17	$94.15	$94.20
Purchase #4	$99.76	3.653%	$103.4042	$103.40	$103.40	$103.40
Purchase #5	$100.53	4.622%	$105.1765	$105.18	$105.20	$105.20
Purchase #6	$165.51	4.260%	$172.5607	$172.56	$172.55	$172.60
Purchase #7	$44.73	4.704%	$46.8341	$46.83	$46.85	$46.80
7 purchase totals =	$565.26		$594.3647	$594.36	$594.40	$594.40