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	$76.42	11.582%	$85.271	$85.27	$85.25	$85.30
Purchase #2	$76.87	4.766%	$80.5336	$80.53	$80.55	$80.50
Purchase #3	$69.53	4.217%	$72.4621	$72.46	$72.45	$72.50
Purchase #4	$13.77	10.289%	$15.1868	$15.19	$15.20	$15.20
Purchase #5	$127.70	13.597%	$145.0634	$145.06	$145.05	$145.10
Purchase #6	$161.86	6.356%	$172.1478	$172.15	$172.15	$172.10
Purchase #7	$122.49	10.129%	$134.897	$134.90	$134.90	$134.90
7 purchase totals =	$648.64		$705.5617	$705.56	$705.55	$705.60