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	$89.39	13.739%	$101.6713	$101.67	$101.65	$101.70
Purchase #2	$46.47	8.507%	$50.4232	$50.42	$50.40	$50.40
Purchase #3	$154.33	12.525%	$173.6598	$173.66	$173.65	$173.70
Purchase #4	$60.71	6.396%	$64.593	$64.59	$64.60	$64.60
Purchase #5	$205.88	4.732%	$215.6222	$215.62	$215.60	$215.60
Purchase #6	$142.28	10.252%	$156.8665	$156.87	$156.85	$156.90
Purchase #7	$185.53	10.789%	$205.5468	$205.55	$205.55	$205.50
7 purchase totals =	$884.59		$968.3828	$968.38	$968.30	$968.40