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	$166.71	13.142%	$188.619	$188.62	$188.60	$188.60
Purchase #2	$245.84	8.485%	$266.6995	$266.70	$266.70	$266.70
Purchase #3	$55.39	7.248%	$59.4047	$59.40	$59.40	$59.40
Purchase #4	$58.47	6.144%	$62.0624	$62.06	$62.05	$62.10
Purchase #5	$232.75	4.637%	$243.5426	$243.54	$243.55	$243.50
Purchase #6	$68.93	5.740%	$72.8866	$72.89	$72.90	$72.90
Purchase #7	$112.61	10.512%	$124.4476	$124.45	$124.45	$124.40
7 purchase totals =	$940.70		$1,017.6624	$1,017.66	$1,017.65	$1,017.60