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	$205.94	13.176%	$233.0747	$233.07	$233.05	$233.10
Purchase #2	$186.89	5.281%	$196.7597	$196.76	$196.75	$196.80
Purchase #3	$66.68	3.831%	$69.2345	$69.23	$69.25	$69.20
Purchase #4	$94.52	6.757%	$100.9067	$100.91	$100.90	$100.90
Purchase #5	$65.41	12.770%	$73.7629	$73.76	$73.75	$73.80
Purchase #6	$135.36	9.768%	$148.582	$148.58	$148.60	$148.60
Purchase #7	$67.37	10.568%	$74.4897	$74.49	$74.50	$74.50
7 purchase totals =	$822.17		$896.8102	$896.80	$896.80	$896.90