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	$98.32	13.353%	$111.4487	$111.45	$111.45	$111.40
Purchase #2	$14.66	4.394%	$15.3042	$15.30	$15.30	$15.30
Purchase #3	$80.30	10.644%	$88.8471	$88.85	$88.85	$88.80
Purchase #4	$131.56	4.213%	$137.1026	$137.10	$137.10	$137.10
Purchase #5	$212.42	11.401%	$236.638	$236.64	$236.65	$236.60
Purchase #6	$100.68	10.833%	$111.5867	$111.59	$111.60	$111.60
Purchase #7	$211.70	12.217%	$237.5634	$237.56	$237.55	$237.60
7 purchase totals =	$849.64		$938.4907	$938.49	$938.50	$938.40