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	$149.78	11.701%	$167.3058	$167.31	$167.30	$167.30
Purchase #2	$82.31	3.582%	$85.2583	$85.26	$85.25	$85.30
Purchase #3	$94.35	12.802%	$106.4287	$106.43	$106.45	$106.40
Purchase #4	$52.94	6.831%	$56.5563	$56.56	$56.55	$56.60
Purchase #5	$141.89	8.532%	$153.9961	$154.00	$154.00	$154.00
Purchase #6	$184.79	4.133%	$192.4274	$192.43	$192.45	$192.40
Purchase #7	$47.98	13.622%	$54.5158	$54.52	$54.50	$54.50
7 purchase totals =	$754.04		$816.4884	$816.51	$816.50	$816.50