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	$162.31	7.140%	$173.8989	$173.90	$173.90	$173.90
Purchase #2	$164.59	6.631%	$175.504	$175.50	$175.50	$175.50
Purchase #3	$231.85	8.334%	$251.1724	$251.17	$251.15	$251.20
Purchase #4	$94.71	11.823%	$105.9076	$105.91	$105.90	$105.90
Purchase #5	$31.71	5.413%	$33.4265	$33.43	$33.45	$33.40
Purchase #6	$42.36	11.659%	$47.2988	$47.30	$47.30	$47.30
Purchase #7	$143.29	8.784%	$155.8766	$155.88	$155.90	$155.90
7 purchase totals =	$870.82		$943.0848	$943.09	$943.10	$943.10