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	$127.35	13.589%	$144.6556	$144.66	$144.65	$144.70
Purchase #2	$243.67	6.782%	$260.1957	$260.20	$260.20	$260.20
Purchase #3	$56.34	4.549%	$58.9029	$58.90	$58.90	$58.90
Purchase #4	$115.68	11.218%	$128.657	$128.66	$128.65	$128.70
Purchase #5	$146.88	4.819%	$153.9581	$153.96	$153.95	$154.00
Purchase #6	$104.51	6.327%	$111.1223	$111.12	$111.10	$111.10
Purchase #7	$131.28	10.157%	$144.6141	$144.61	$144.60	$144.60
7 purchase totals =	$925.71		$1,002.1057	$1,002.11	$1,002.05	$1,002.20