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	$215.30	7.873%	$232.2506	$232.25	$232.25	$232.30
Purchase #2	$141.52	7.553%	$152.209	$152.21	$152.20	$152.20
Purchase #3	$207.31	3.606%	$214.7856	$214.79	$214.80	$214.80
Purchase #4	$119.28	7.689%	$128.4514	$128.45	$128.45	$128.50
Purchase #5	$88.25	12.525%	$99.3033	$99.30	$99.30	$99.30
Purchase #6	$81.65	10.421%	$90.1587	$90.16	$90.15	$90.20
Purchase #7	$141.84	8.763%	$154.2694	$154.27	$154.25	$154.30
7 purchase totals =	$995.15		$1,071.4280	$1,071.43	$1,071.40	$1,071.60