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	$151.85	3.389%	$156.9962	$157.00	$157.00	$157.00
Purchase #2	$197.73	3.485%	$204.6209	$204.62	$204.60	$204.60
Purchase #3	$83.33	7.824%	$89.8497	$89.85	$89.85	$89.80
Purchase #4	$116.44	11.863%	$130.2533	$130.25	$130.25	$130.30
Purchase #5	$117.54	8.405%	$127.4192	$127.42	$127.40	$127.40
Purchase #6	$106.39	8.555%	$115.4917	$115.49	$115.50	$115.50
Purchase #7	$158.41	12.481%	$178.1812	$178.18	$178.20	$178.20
7 purchase totals =	$931.69		$1,002.8122	$1,002.81	$1,002.80	$1,002.80