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	$73.53	13.653%	$83.5691	$83.57	$83.55	$83.60
Purchase #2	$139.82	4.825%	$146.5663	$146.57	$146.55	$146.60
Purchase #3	$232.31	4.226%	$242.1274	$242.13	$242.15	$242.10
Purchase #4	$200.62	7.390%	$215.4458	$215.45	$215.45	$215.40
Purchase #5	$10.55	12.331%	$11.8509	$11.85	$11.85	$11.90
Purchase #6	$248.69	9.472%	$272.2459	$272.25	$272.25	$272.20
Purchase #7	$220.58	13.461%	$250.2723	$250.27	$250.25	$250.30
7 purchase totals =	$1,126.10		$1,222.0777	$1,222.09	$1,222.05	$1,222.10