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	$153.87	11.225%	$171.1419	$171.14	$171.15	$171.10
Purchase #2	$88.41	5.632%	$93.3893	$93.39	$93.40	$93.40
Purchase #3	$18.76	5.819%	$19.8516	$19.85	$19.85	$19.90
Purchase #4	$149.58	5.833%	$158.305	$158.31	$158.30	$158.30
Purchase #5	$100.83	9.602%	$110.5117	$110.51	$110.50	$110.50
Purchase #6	$225.44	12.421%	$253.4419	$253.44	$253.45	$253.40
Purchase #7	$245.71	3.803%	$255.0544	$255.05	$255.05	$255.10
7 purchase totals =	$982.60		$1,061.6958	$1,061.69	$1,061.70	$1,061.70