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	$154.52	7.185%	$165.6223	$165.62	$165.60	$165.60
Purchase #2	$200.58	11.425%	$223.4963	$223.50	$223.50	$223.50
Purchase #3	$77.67	6.320%	$82.5787	$82.58	$82.60	$82.60
Purchase #4	$130.40	12.302%	$146.4418	$146.44	$146.45	$146.40
Purchase #5	$48.52	5.732%	$51.3012	$51.30	$51.30	$51.30
Purchase #6	$109.32	7.701%	$117.7387	$117.74	$117.75	$117.70
Purchase #7	$140.46	10.422%	$155.0987	$155.10	$155.10	$155.10
7 purchase totals =	$861.47		$942.2777	$942.28	$942.30	$942.20