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	$153.50	3.244%	$158.4795	$158.48	$158.50	$158.50
Purchase #2	$141.97	6.316%	$150.9368	$150.94	$150.95	$150.90
Purchase #3	$175.99	13.151%	$199.1344	$199.13	$199.15	$199.10
Purchase #4	$105.73	7.201%	$113.3436	$113.34	$113.35	$113.30
Purchase #5	$46.38	9.133%	$50.6159	$50.62	$50.60	$50.60
Purchase #6	$233.39	7.142%	$250.0587	$250.06	$250.05	$250.10
Purchase #7	$167.47	9.285%	$183.0196	$183.02	$183.00	$183.00
7 purchase totals =	$1,024.43		$1,105.5885	$1,105.59	$1,105.60	$1,105.50