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	$119.52	3.600%	$123.8227	$123.82	$123.80	$123.80
Purchase #2	$230.37	7.333%	$247.263	$247.26	$247.25	$247.30
Purchase #3	$22.87	10.464%	$25.2631	$25.26	$25.25	$25.30
Purchase #4	$241.32	4.184%	$251.4168	$251.42	$251.40	$251.40
Purchase #5	$41.90	7.742%	$45.1439	$45.14	$45.15	$45.10
Purchase #6	$79.81	7.730%	$85.9793	$85.98	$86.00	$86.00
Purchase #7	$124.79	11.750%	$139.4528	$139.45	$139.45	$139.50
7 purchase totals =	$860.58		$918.3416	$918.33	$918.30	$918.40