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	$132.30	4.834%	$138.6954	$138.70	$138.70	$138.70
Purchase #2	$139.86	8.488%	$151.7313	$151.73	$151.75	$151.70
Purchase #3	$118.48	7.323%	$127.1563	$127.16	$127.15	$127.20
Purchase #4	$116.66	10.361%	$128.7471	$128.75	$128.75	$128.70
Purchase #5	$183.88	6.546%	$195.9168	$195.92	$195.90	$195.90
Purchase #6	$103.27	7.553%	$111.07	$111.07	$111.05	$111.10
Purchase #7	$208.46	7.375%	$223.8339	$223.83	$223.85	$223.80
7 purchase totals =	$1,002.91		$1,077.1508	$1,077.16	$1,077.15	$1,077.10