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	$43.80	10.712%	$48.4919	$48.49	$48.50	$48.50
Purchase #2	$72.35	13.624%	$82.207	$82.21	$82.20	$82.20
Purchase #3	$85.45	12.409%	$96.0535	$96.05	$96.05	$96.10
Purchase #4	$201.94	10.401%	$222.9438	$222.94	$222.95	$222.90
Purchase #5	$127.58	13.313%	$144.5647	$144.56	$144.55	$144.60
Purchase #6	$179.96	8.509%	$195.2728	$195.27	$195.25	$195.30
Purchase #7	$91.54	4.799%	$95.933	$95.93	$95.95	$95.90
7 purchase totals =	$802.62		$885.4667	$885.45	$885.45	$885.50