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	$61.66	11.689%	$68.8674	$68.87	$68.85	$68.90
Purchase #2	$105.31	8.164%	$113.9075	$113.91	$113.90	$113.90
Purchase #3	$12.47	7.524%	$13.4082	$13.41	$13.40	$13.40
Purchase #4	$175.68	13.432%	$199.2773	$199.28	$199.30	$199.30
Purchase #5	$155.80	11.376%	$173.5238	$173.52	$173.50	$173.50
Purchase #6	$147.32	3.451%	$152.404	$152.40	$152.40	$152.40
Purchase #7	$191.45	13.590%	$217.4681	$217.47	$217.45	$217.50
7 purchase totals =	$849.69		$938.8563	$938.86	$938.80	$938.90