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	$84.68	5.858%	$89.6406	$89.64	$89.65	$89.60
Purchase #2	$144.75	8.642%	$157.2593	$157.26	$157.25	$157.30
Purchase #3	$35.83	7.294%	$38.4434	$38.44	$38.45	$38.40
Purchase #4	$43.37	8.222%	$46.9359	$46.94	$46.95	$46.90
Purchase #5	$173.94	4.352%	$181.5099	$181.51	$181.50	$181.50
Purchase #6	$97.40	12.857%	$109.9227	$109.92	$109.90	$109.90
Purchase #7	$215.40	3.358%	$222.6331	$222.63	$222.65	$222.60
7 purchase totals =	$795.37		$846.3449	$846.34	$846.35	$846.20