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	$144.40	4.526%	$150.9355	$150.94	$150.95	$150.90
Purchase #2	$193.47	11.719%	$216.1427	$216.14	$216.15	$216.10
Purchase #3	$112.94	4.643%	$118.1838	$118.18	$118.20	$118.20
Purchase #4	$46.72	11.600%	$52.1395	$52.14	$52.15	$52.10
Purchase #5	$37.61	13.605%	$42.7268	$42.73	$42.75	$42.70
Purchase #6	$172.77	11.445%	$192.5435	$192.54	$192.55	$192.50
Purchase #7	$216.72	5.411%	$228.4467	$228.45	$228.45	$228.40
7 purchase totals =	$924.63		$1,001.1185	$1,001.12	$1,001.20	$1,000.90