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	$181.49	7.473%	$195.0527	$195.05	$195.05	$195.10
Purchase #2	$99.84	11.569%	$111.3905	$111.39	$111.40	$111.40
Purchase #3	$131.40	5.399%	$138.4943	$138.49	$138.50	$138.50
Purchase #4	$111.43	8.604%	$121.0174	$121.02	$121.00	$121.00
Purchase #5	$106.37	5.160%	$111.8587	$111.86	$111.85	$111.90
Purchase #6	$172.67	7.588%	$185.7722	$185.77	$185.75	$185.80
Purchase #7	$16.38	9.772%	$17.9807	$17.98	$18.00	$18.00
7 purchase totals =	$819.58		$881.5665	$881.56	$881.55	$881.70