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	$117.80	7.489%	$126.622	$126.62	$126.60	$126.60
Purchase #2	$65.80	11.350%	$73.2683	$73.27	$73.25	$73.30
Purchase #3	$249.49	6.108%	$264.7288	$264.73	$264.75	$264.70
Purchase #4	$132.33	10.577%	$146.3265	$146.33	$146.35	$146.30
Purchase #5	$43.51	4.340%	$45.3983	$45.40	$45.40	$45.40
Purchase #6	$19.73	5.779%	$20.8702	$20.87	$20.85	$20.90
Purchase #7	$83.50	3.589%	$86.4968	$86.50	$86.50	$86.50
7 purchase totals =	$712.16		$763.7109	$763.72	$763.70	$763.70