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	$16.50	3.161%	$17.0216	$17.02	$17.00	$17.00
Purchase #2	$61.39	6.809%	$65.57	$65.57	$65.55	$65.60
Purchase #3	$107.61	9.211%	$117.522	$117.52	$117.50	$117.50
Purchase #4	$108.91	13.357%	$123.4571	$123.46	$123.45	$123.50
Purchase #5	$234.30	13.494%	$265.9164	$265.92	$265.90	$265.90
Purchase #6	$77.91	5.586%	$82.2621	$82.26	$82.25	$82.30
Purchase #7	$118.60	4.829%	$124.3272	$124.33	$124.35	$124.30
7 purchase totals =	$725.22		$796.0764	$796.08	$796.00	$796.10