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	$244.72	13.513%	$277.789	$277.79	$277.80	$277.80
Purchase #2	$122.50	6.707%	$130.7161	$130.72	$130.70	$130.70
Purchase #3	$36.99	5.153%	$38.8961	$38.90	$38.90	$38.90
Purchase #4	$84.33	6.537%	$89.8427	$89.84	$89.85	$89.80
Purchase #5	$49.46	5.153%	$52.0087	$52.01	$52.00	$52.00
Purchase #6	$164.56	10.451%	$181.7582	$181.76	$181.75	$181.80
Purchase #7	$157.30	3.396%	$162.6419	$162.64	$162.65	$162.60
7 purchase totals =	$859.86		$933.6527	$933.66	$933.65	$933.60