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	$137.38	10.199%	$151.3914	$151.39	$151.40	$151.40
Purchase #2	$14.65	4.478%	$15.306	$15.31	$15.30	$15.30
Purchase #3	$118.65	7.230%	$127.2284	$127.23	$127.25	$127.20
Purchase #4	$90.78	4.772%	$95.112	$95.11	$95.10	$95.10
Purchase #5	$174.86	8.832%	$190.3036	$190.30	$190.30	$190.30
Purchase #6	$211.61	5.244%	$222.7068	$222.71	$222.70	$222.70
Purchase #7	$217.57	11.279%	$242.1097	$242.11	$242.10	$242.10
7 purchase totals =	$965.50		$1,044.1579	$1,044.16	$1,044.15	$1,044.10