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	$80.63	6.446%	$85.8274	$85.83	$85.85	$85.80
Purchase #2	$123.90	5.196%	$130.3378	$130.34	$130.35	$130.30
Purchase #3	$16.54	3.119%	$17.0559	$17.06	$17.05	$17.10
Purchase #4	$102.89	13.163%	$116.4334	$116.43	$116.45	$116.40
Purchase #5	$58.58	8.857%	$63.7684	$63.77	$63.75	$63.80
Purchase #6	$152.52	6.651%	$162.6641	$162.66	$162.65	$162.70
Purchase #7	$56.58	5.585%	$59.74	$59.74	$59.75	$59.70
7 purchase totals =	$591.64		$635.8270	$635.83	$635.85	$635.80