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	$144.37	8.698%	$156.9273	$156.93	$156.95	$156.90
Purchase #2	$139.83	10.618%	$154.6771	$154.68	$154.70	$154.70
Purchase #3	$169.29	10.147%	$186.4679	$186.47	$186.45	$186.50
Purchase #4	$65.61	10.367%	$72.4118	$72.41	$72.40	$72.40
Purchase #5	$100.34	3.586%	$103.9382	$103.94	$103.95	$103.90
Purchase #6	$32.96	10.779%	$36.5128	$36.51	$36.50	$36.50
Purchase #7	$18.95	11.140%	$21.061	$21.06	$21.05	$21.10
7 purchase totals =	$671.35		$731.9961	$732.00	$732.00	$732.00