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	$141.82	6.798%	$151.4609	$151.46	$151.45	$151.50
Purchase #2	$218.62	5.547%	$230.7469	$230.75	$230.75	$230.70
Purchase #3	$75.76	10.520%	$83.73	$83.73	$83.75	$83.70
Purchase #4	$56.89	12.600%	$64.0581	$64.06	$64.05	$64.10
Purchase #5	$96.60	6.787%	$103.1562	$103.16	$103.15	$103.20
Purchase #6	$231.66	4.359%	$241.7581	$241.76	$241.75	$241.80
Purchase #7	$196.55	4.390%	$205.1785	$205.18	$205.20	$205.20
7 purchase totals =	$1,017.90		$1,080.0887	$1,080.10	$1,080.10	$1,080.20