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	$216.59	7.848%	$233.588	$233.59	$233.60	$233.60
Purchase #2	$17.66	6.525%	$18.8123	$18.81	$18.80	$18.80
Purchase #3	$7.76	12.499%	$8.7299	$8.73	$8.75	$8.70
Purchase #4	$48.76	3.396%	$50.4159	$50.42	$50.40	$50.40
Purchase #5	$97.44	8.689%	$105.9066	$105.91	$105.90	$105.90
Purchase #6	$239.33	6.184%	$254.1302	$254.13	$254.15	$254.10
Purchase #7	$81.53	9.240%	$89.0634	$89.06	$89.05	$89.10
7 purchase totals =	$709.07		$760.6463	$760.65	$760.65	$760.60