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	$179.94	3.321%	$185.9158	$185.92	$185.90	$185.90
Purchase #2	$135.75	3.331%	$140.2718	$140.27	$140.25	$140.30
Purchase #3	$207.69	5.857%	$219.8544	$219.85	$219.85	$219.90
Purchase #4	$137.52	5.806%	$145.5044	$145.50	$145.50	$145.50
Purchase #5	$121.87	6.329%	$129.5832	$129.58	$129.60	$129.60
Purchase #6	$227.79	8.690%	$247.585	$247.59	$247.60	$247.60
Purchase #7	$94.72	5.441%	$99.8737	$99.87	$99.85	$99.90
7 purchase totals =	$1,105.28		$1,168.5883	$1,168.58	$1,168.55	$1,168.70