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	$198.86	12.502%	$223.7215	$223.72	$223.70	$223.70
Purchase #2	$209.64	10.796%	$232.2727	$232.27	$232.25	$232.30
Purchase #3	$17.76	13.525%	$20.162	$20.16	$20.15	$20.20
Purchase #4	$66.26	5.701%	$70.0375	$70.04	$70.05	$70.00
Purchase #5	$83.68	10.399%	$92.3819	$92.38	$92.40	$92.40
Purchase #6	$53.96	9.859%	$59.2799	$59.28	$59.30	$59.30
Purchase #7	$148.82	6.683%	$158.7656	$158.77	$158.75	$158.80
7 purchase totals =	$778.98		$856.6211	$856.62	$856.60	$856.70