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	$219.57	6.504%	$233.8508	$233.85	$233.85	$233.90
Purchase #2	$67.43	7.368%	$72.3982	$72.40	$72.40	$72.40
Purchase #3	$99.79	3.531%	$103.3136	$103.31	$103.30	$103.30
Purchase #4	$154.31	6.584%	$164.4698	$164.47	$164.45	$164.50
Purchase #5	$65.65	6.434%	$69.8739	$69.87	$69.85	$69.90
Purchase #6	$164.38	10.254%	$181.2355	$181.24	$181.25	$181.20
Purchase #7	$128.57	12.834%	$145.0707	$145.07	$145.05	$145.10
7 purchase totals =	$899.70		$970.2125	$970.21	$970.15	$970.30