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	$90.91	10.725%	$100.6601	$100.66	$100.65	$100.70
Purchase #2	$149.79	13.169%	$169.5158	$169.52	$169.50	$169.50
Purchase #3	$22.91	5.802%	$24.2392	$24.24	$24.25	$24.20
Purchase #4	$221.66	10.717%	$245.4153	$245.42	$245.40	$245.40
Purchase #5	$127.72	3.135%	$131.724	$131.72	$131.70	$131.70
Purchase #6	$69.69	12.849%	$78.6445	$78.64	$78.65	$78.60
Purchase #7	$15.90	4.801%	$16.6634	$16.66	$16.65	$16.70
7 purchase totals =	$698.58		$766.8623	$766.86	$766.80	$766.80