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	$94.61	9.338%	$103.4447	$103.44	$103.45	$103.40
Purchase #2	$70.37	3.587%	$72.8942	$72.89	$72.90	$72.90
Purchase #3	$37.87	11.794%	$42.3364	$42.34	$42.35	$42.30
Purchase #4	$52.75	8.388%	$57.1747	$57.17	$57.15	$57.20
Purchase #5	$103.73	5.290%	$109.2173	$109.22	$109.20	$109.20
Purchase #6	$227.50	11.799%	$254.3427	$254.34	$254.35	$254.30
Purchase #7	$11.30	11.653%	$12.6168	$12.62	$12.60	$12.60
7 purchase totals =	$598.13		$652.0268	$652.02	$652.00	$651.90