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	$46.71	7.773%	$50.3408	$50.34	$50.35	$50.30
Purchase #2	$104.38	8.853%	$113.6208	$113.62	$113.60	$113.60
Purchase #3	$181.71	7.107%	$194.6241	$194.62	$194.60	$194.60
Purchase #4	$208.30	6.804%	$222.4727	$222.47	$222.45	$222.50
Purchase #5	$242.79	3.421%	$251.0958	$251.10	$251.10	$251.10
Purchase #6	$77.74	5.495%	$82.0118	$82.01	$82.00	$82.00
Purchase #7	$107.74	3.702%	$111.7285	$111.73	$111.75	$111.70
7 purchase totals =	$969.37		$1,025.8945	$1,025.89	$1,025.85	$1,025.80