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	$136.77	5.350%	$144.0872	$144.09	$144.10	$144.10
Purchase #2	$173.65	8.166%	$187.8303	$187.83	$187.85	$187.80
Purchase #3	$18.84	8.132%	$20.3721	$20.37	$20.35	$20.40
Purchase #4	$76.52	6.158%	$81.2321	$81.23	$81.25	$81.20
Purchase #5	$89.75	3.544%	$92.9307	$92.93	$92.95	$92.90
Purchase #6	$87.60	13.627%	$99.5373	$99.54	$99.55	$99.50
Purchase #7	$101.32	4.858%	$106.2421	$106.24	$106.25	$106.20
7 purchase totals =	$684.45		$732.2318	$732.23	$732.30	$732.10