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	$206.49	11.349%	$229.9246	$229.92	$229.90	$229.90
Purchase #2	$244.50	7.205%	$262.1162	$262.12	$262.10	$262.10
Purchase #3	$73.97	4.665%	$77.4207	$77.42	$77.40	$77.40
Purchase #4	$206.66	8.250%	$223.7095	$223.71	$223.70	$223.70
Purchase #5	$9.80	10.722%	$10.8508	$10.85	$10.85	$10.90
Purchase #6	$121.37	5.140%	$127.6084	$127.61	$127.60	$127.60
Purchase #7	$96.87	3.140%	$99.9117	$99.91	$99.90	$99.90
7 purchase totals =	$959.66		$1,031.5419	$1,031.54	$1,031.45	$1,031.50