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	$99.58	9.290%	$108.831	$108.83	$108.85	$108.80
Purchase #2	$220.55	8.263%	$238.774	$238.77	$238.75	$238.80
Purchase #3	$64.38	11.417%	$71.7303	$71.73	$71.75	$71.70
Purchase #4	$59.66	4.220%	$62.1777	$62.18	$62.20	$62.20
Purchase #5	$114.87	10.831%	$127.3116	$127.31	$127.30	$127.30
Purchase #6	$172.86	4.212%	$180.1409	$180.14	$180.15	$180.10
Purchase #7	$141.52	5.340%	$149.0772	$149.08	$149.10	$149.10
7 purchase totals =	$873.42		$938.0427	$938.04	$938.10	$938.00