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	$124.54	10.767%	$137.9492	$137.95	$137.95	$137.90
Purchase #2	$60.31	12.147%	$67.6359	$67.64	$67.65	$67.60
Purchase #3	$133.69	7.824%	$144.1499	$144.15	$144.15	$144.10
Purchase #4	$173.25	6.387%	$184.3155	$184.32	$184.30	$184.30
Purchase #5	$203.73	8.249%	$220.5357	$220.54	$220.55	$220.50
Purchase #6	$181.75	9.806%	$199.5724	$199.57	$199.55	$199.60
Purchase #7	$131.77	10.541%	$145.6599	$145.66	$145.65	$145.70
7 purchase totals =	$1,009.04		$1,099.8185	$1,099.83	$1,099.80	$1,099.70