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	$100.52	11.855%	$112.4366	$112.44	$112.45	$112.40
Purchase #2	$100.98	8.174%	$109.2341	$109.23	$109.25	$109.20
Purchase #3	$74.72	4.561%	$78.128	$78.13	$78.15	$78.10
Purchase #4	$119.84	8.589%	$130.1331	$130.13	$130.15	$130.10
Purchase #5	$241.62	5.458%	$254.8076	$254.81	$254.80	$254.80
Purchase #6	$234.51	7.149%	$251.2751	$251.28	$251.30	$251.30
Purchase #7	$93.63	7.147%	$100.3217	$100.32	$100.30	$100.30
7 purchase totals =	$965.82		$1,036.3362	$1,036.34	$1,036.40	$1,036.20