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	$182.45	8.669%	$198.2666	$198.27	$198.25	$198.30
Purchase #2	$30.83	6.305%	$32.7738	$32.77	$32.75	$32.80
Purchase #3	$242.71	13.406%	$275.2477	$275.25	$275.25	$275.20
Purchase #4	$26.79	3.745%	$27.7933	$27.79	$27.80	$27.80
Purchase #5	$85.94	13.719%	$97.7301	$97.73	$97.75	$97.70
Purchase #6	$244.42	8.381%	$264.9048	$264.90	$264.90	$264.90
Purchase #7	$143.47	10.627%	$158.7166	$158.72	$158.70	$158.70
7 purchase totals =	$956.61		$1,055.4329	$1,055.43	$1,055.40	$1,055.40