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	$14.30	5.368%	$15.0676	$15.07	$15.05	$15.10
Purchase #2	$101.70	9.648%	$111.512	$111.51	$111.50	$111.50
Purchase #3	$240.90	11.680%	$269.0371	$269.04	$269.05	$269.00
Purchase #4	$51.86	5.328%	$54.6231	$54.62	$54.60	$54.60
Purchase #5	$157.31	12.264%	$176.6025	$176.60	$176.60	$176.60
Purchase #6	$199.74	9.221%	$218.158	$218.16	$218.15	$218.20
Purchase #7	$214.89	11.823%	$240.2964	$240.30	$240.30	$240.30
7 purchase totals =	$980.70		$1,085.2967	$1,085.30	$1,085.25	$1,085.30