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	$154.26	7.509%	$165.8434	$165.84	$165.85	$165.80
Purchase #2	$105.64	8.301%	$114.4092	$114.41	$114.40	$114.40
Purchase #3	$19.26	7.258%	$20.6579	$20.66	$20.65	$20.70
Purchase #4	$97.83	7.583%	$105.2484	$105.25	$105.25	$105.20
Purchase #5	$82.69	8.254%	$89.5152	$89.52	$89.50	$89.50
Purchase #6	$185.32	7.450%	$199.1263	$199.13	$199.15	$199.10
Purchase #7	$21.40	5.805%	$22.6423	$22.64	$22.65	$22.60
7 purchase totals =	$666.40		$717.4427	$717.45	$717.45	$717.30