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	$143.78	7.562%	$154.6526	$154.65	$154.65	$154.70
Purchase #2	$28.66	11.135%	$31.8513	$31.85	$31.85	$31.90
Purchase #3	$14.34	5.510%	$15.1301	$15.13	$15.15	$15.10
Purchase #4	$148.66	4.162%	$154.8472	$154.85	$154.85	$154.80
Purchase #5	$209.72	3.638%	$217.3496	$217.35	$217.35	$217.30
Purchase #6	$90.28	10.621%	$99.8686	$99.87	$99.85	$99.90
Purchase #7	$138.57	9.404%	$151.6011	$151.60	$151.60	$151.60
7 purchase totals =	$774.01		$825.3005	$825.30	$825.30	$825.30