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	$152.50	6.424%	$162.2966	$162.30	$162.30	$162.30
Purchase #2	$108.29	8.520%	$117.5163	$117.52	$117.50	$117.50
Purchase #3	$133.32	5.861%	$141.1339	$141.13	$141.15	$141.10
Purchase #4	$97.36	6.765%	$103.9464	$103.95	$103.95	$103.90
Purchase #5	$206.62	7.634%	$222.3934	$222.39	$222.40	$222.40
Purchase #6	$153.88	8.625%	$167.1522	$167.15	$167.15	$167.20
Purchase #7	$233.98	10.518%	$258.59	$258.59	$258.60	$258.60
7 purchase totals =	$1,085.95		$1,173.0288	$1,173.03	$1,173.05	$1,173.00