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	$141.75	11.376%	$157.8755	$157.88	$157.90	$157.90
Purchase #2	$134.37	3.195%	$138.6631	$138.66	$138.65	$138.70
Purchase #3	$142.34	6.751%	$151.9494	$151.95	$151.95	$151.90
Purchase #4	$100.62	11.139%	$111.8281	$111.83	$111.85	$111.80
Purchase #5	$63.57	10.819%	$70.4476	$70.45	$70.45	$70.40
Purchase #6	$81.42	8.399%	$88.2585	$88.26	$88.25	$88.30
Purchase #7	$93.79	12.295%	$105.3215	$105.32	$105.30	$105.30
7 purchase totals =	$757.86		$824.3437	$824.35	$824.35	$824.30