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	$138.78	4.536%	$145.0751	$145.08	$145.10	$145.10
Purchase #2	$16.92	4.460%	$17.6746	$17.67	$17.65	$17.70
Purchase #3	$28.96	6.234%	$30.7654	$30.77	$30.75	$30.80
Purchase #4	$55.78	10.189%	$61.4634	$61.46	$61.45	$61.50
Purchase #5	$29.44	11.743%	$32.8971	$32.90	$32.90	$32.90
Purchase #6	$80.31	13.147%	$90.8684	$90.87	$90.85	$90.90
Purchase #7	$108.92	10.386%	$120.2324	$120.23	$120.25	$120.20
7 purchase totals =	$459.11		$498.9764	$498.98	$498.95	$499.10