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	$90.92	9.627%	$99.6729	$99.67	$99.65	$99.70
Purchase #2	$14.78	10.244%	$16.2941	$16.29	$16.30	$16.30
Purchase #3	$50.82	6.832%	$54.292	$54.29	$54.30	$54.30
Purchase #4	$101.26	3.110%	$104.4092	$104.41	$104.40	$104.40
Purchase #5	$107.31	3.598%	$111.171	$111.17	$111.15	$111.20
Purchase #6	$76.82	13.358%	$87.0816	$87.08	$87.10	$87.10
Purchase #7	$175.45	13.799%	$199.6603	$199.66	$199.65	$199.70
7 purchase totals =	$617.36		$672.5811	$672.57	$672.55	$672.70