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	$89.25	12.501%	$100.4071	$100.41	$100.40	$100.40
Purchase #2	$153.67	13.259%	$174.0451	$174.05	$174.05	$174.00
Purchase #3	$239.93	6.608%	$255.7846	$255.78	$255.80	$255.80
Purchase #4	$49.90	6.699%	$53.2428	$53.24	$53.25	$53.20
Purchase #5	$131.94	8.843%	$143.6075	$143.61	$143.60	$143.60
Purchase #6	$115.96	9.799%	$127.3229	$127.32	$127.30	$127.30
Purchase #7	$181.73	5.813%	$192.294	$192.29	$192.30	$192.30
7 purchase totals =	$962.38		$1,046.7040	$1,046.70	$1,046.70	$1,046.60