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	$196.29	8.198%	$212.3819	$212.38	$212.40	$212.40
Purchase #2	$130.99	5.120%	$137.6967	$137.70	$137.70	$137.70
Purchase #3	$168.30	6.728%	$179.6232	$179.62	$179.60	$179.60
Purchase #4	$90.82	12.564%	$102.2306	$102.23	$102.25	$102.20
Purchase #5	$40.54	13.135%	$45.8649	$45.86	$45.85	$45.90
Purchase #6	$52.78	13.359%	$59.8309	$59.83	$59.85	$59.80
Purchase #7	$249.55	10.271%	$275.1813	$275.18	$275.20	$275.20
7 purchase totals =	$929.27		$1,012.8095	$1,012.80	$1,012.85	$1,012.80