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	$32.96	5.602%	$34.8064	$34.81	$34.80	$34.80
Purchase #2	$165.29	5.360%	$174.1495	$174.15	$174.15	$174.10
Purchase #3	$191.35	4.353%	$199.6795	$199.68	$199.70	$199.70
Purchase #4	$145.26	11.426%	$161.8574	$161.86	$161.85	$161.90
Purchase #5	$98.61	12.862%	$111.2932	$111.29	$111.30	$111.30
Purchase #6	$61.96	13.847%	$70.5396	$70.54	$70.55	$70.50
Purchase #7	$100.98	8.862%	$109.9288	$109.93	$109.95	$109.90
7 purchase totals =	$796.41		$862.2544	$862.26	$862.30	$862.20