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	$249.45	10.841%	$276.4929	$276.49	$276.50	$276.50
Purchase #2	$9.75	11.162%	$10.8383	$10.84	$10.85	$10.80
Purchase #3	$191.79	6.510%	$204.2755	$204.28	$204.30	$204.30
Purchase #4	$122.62	3.832%	$127.3188	$127.32	$127.30	$127.30
Purchase #5	$168.47	10.746%	$186.5738	$186.57	$186.55	$186.60
Purchase #6	$17.27	9.384%	$18.8906	$18.89	$18.90	$18.90
Purchase #7	$216.59	8.419%	$234.8247	$234.82	$234.80	$234.80
7 purchase totals =	$975.94		$1,059.2146	$1,059.21	$1,059.20	$1,059.20