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	$85.94	11.531%	$95.8497	$95.85	$95.85	$95.80
Purchase #2	$48.99	9.222%	$53.5079	$53.51	$53.50	$53.50
Purchase #3	$125.25	7.785%	$135.0007	$135.00	$135.00	$135.00
Purchase #4	$118.56	7.809%	$127.8184	$127.82	$127.80	$127.80
Purchase #5	$45.72	12.873%	$51.6055	$51.61	$51.60	$51.60
Purchase #6	$11.27	13.503%	$12.7918	$12.79	$12.80	$12.80
Purchase #7	$31.91	6.549%	$33.9998	$34.00	$34.00	$34.00
7 purchase totals =	$467.64		$510.5738	$510.58	$510.55	$510.50