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	$108.71	13.619%	$123.5152	$123.52	$123.50	$123.50
Purchase #2	$48.83	8.624%	$53.0411	$53.04	$53.05	$53.00
Purchase #3	$28.77	13.591%	$32.6801	$32.68	$32.70	$32.70
Purchase #4	$49.35	4.427%	$51.5347	$51.53	$51.55	$51.50
Purchase #5	$184.84	11.302%	$205.7306	$205.73	$205.75	$205.70
Purchase #6	$38.98	3.109%	$40.1919	$40.19	$40.20	$40.20
Purchase #7	$191.38	10.549%	$211.5687	$211.57	$211.55	$211.60
7 purchase totals =	$650.86		$718.2623	$718.26	$718.30	$718.20