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	$185.33	10.679%	$205.1214	$205.12	$205.10	$205.10
Purchase #2	$86.61	13.159%	$98.007	$98.01	$98.00	$98.00
Purchase #3	$228.52	11.161%	$254.0251	$254.03	$254.05	$254.00
Purchase #4	$164.32	7.470%	$176.5947	$176.59	$176.60	$176.60
Purchase #5	$195.68	9.595%	$214.4555	$214.46	$214.45	$214.50
Purchase #6	$247.42	9.642%	$271.2762	$271.28	$271.30	$271.30
Purchase #7	$100.71	10.696%	$111.4819	$111.48	$111.50	$111.50
7 purchase totals =	$1,208.59		$1,330.9618	$1,330.97	$1,331.00	$1,331.00