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	$179.81	4.485%	$187.8745	$187.87	$187.85	$187.90
Purchase #2	$138.25	9.244%	$151.0298	$151.03	$151.05	$151.00
Purchase #3	$9.49	6.461%	$10.1031	$10.10	$10.10	$10.10
Purchase #4	$96.43	10.430%	$106.4876	$106.49	$106.50	$106.50
Purchase #5	$108.56	13.534%	$123.2525	$123.25	$123.25	$123.30
Purchase #6	$144.69	12.537%	$162.8298	$162.83	$162.85	$162.80
Purchase #7	$24.26	6.837%	$25.9187	$25.92	$25.90	$25.90
7 purchase totals =	$701.49		$767.4960	$767.49	$767.50	$767.50