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	$141.51	12.170%	$158.7318	$158.73	$158.75	$158.70
Purchase #2	$126.71	10.606%	$140.1489	$140.15	$140.15	$140.10
Purchase #3	$26.78	12.103%	$30.0212	$30.02	$30.00	$30.00
Purchase #4	$126.32	12.120%	$141.63	$141.63	$141.65	$141.60
Purchase #5	$116.44	9.603%	$127.6217	$127.62	$127.60	$127.60
Purchase #6	$193.43	13.685%	$219.9009	$219.90	$219.90	$219.90
Purchase #7	$61.79	9.404%	$67.6007	$67.60	$67.60	$67.60
7 purchase totals =	$792.98		$885.6552	$885.65	$885.65	$885.50