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	$137.29	13.188%	$155.3958	$155.40	$155.40	$155.40
Purchase #2	$74.71	4.729%	$78.243	$78.24	$78.25	$78.20
Purchase #3	$146.74	7.806%	$158.1945	$158.19	$158.20	$158.20
Purchase #4	$92.67	9.484%	$101.4588	$101.46	$101.45	$101.50
Purchase #5	$155.87	7.430%	$167.4511	$167.45	$167.45	$167.50
Purchase #6	$178.26	11.810%	$199.3125	$199.31	$199.30	$199.30
Purchase #7	$143.41	10.109%	$157.9073	$157.91	$157.90	$157.90
7 purchase totals =	$928.95		$1,017.9630	$1,017.96	$1,017.95	$1,018.00