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	$68.32	4.175%	$71.1724	$71.17	$71.15	$71.20
Purchase #2	$23.94	5.705%	$25.3058	$25.31	$25.30	$25.30
Purchase #3	$111.41	13.345%	$126.2777	$126.28	$126.30	$126.30
Purchase #4	$134.46	11.410%	$149.8019	$149.80	$149.80	$149.80
Purchase #5	$21.92	4.134%	$22.8262	$22.83	$22.85	$22.80
Purchase #6	$214.25	4.820%	$224.5769	$224.58	$224.60	$224.60
Purchase #7	$123.60	6.363%	$131.4647	$131.46	$131.45	$131.50
7 purchase totals =	$697.90		$751.4256	$751.43	$751.45	$751.50