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	$96.34	9.525%	$105.5164	$105.52	$105.50	$105.50
Purchase #2	$139.77	8.376%	$151.4771	$151.48	$151.50	$151.50
Purchase #3	$54.61	4.822%	$57.2433	$57.24	$57.25	$57.20
Purchase #4	$79.47	5.437%	$83.7908	$83.79	$83.80	$83.80
Purchase #5	$24.63	12.406%	$27.6856	$27.69	$27.70	$27.70
Purchase #6	$117.26	13.712%	$133.3387	$133.34	$133.35	$133.30
Purchase #7	$145.33	7.835%	$156.7166	$156.72	$156.70	$156.70
7 purchase totals =	$657.41		$715.7685	$715.78	$715.80	$715.70