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	$144.69	5.826%	$153.1196	$153.12	$153.10	$153.10
Purchase #2	$121.78	13.239%	$137.9025	$137.90	$137.90	$137.90
Purchase #3	$139.26	9.304%	$152.2168	$152.22	$152.20	$152.20
Purchase #4	$123.49	7.232%	$132.4208	$132.42	$132.40	$132.40
Purchase #5	$117.66	8.236%	$127.3505	$127.35	$127.35	$127.40
Purchase #6	$121.55	8.802%	$132.2488	$132.25	$132.25	$132.20
Purchase #7	$222.46	13.786%	$253.1283	$253.13	$253.15	$253.10
7 purchase totals =	$990.89		$1,088.3873	$1,088.39	$1,088.35	$1,088.30