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	$168.73	7.762%	$181.8268	$181.83	$181.85	$181.80
Purchase #2	$100.40	13.714%	$114.1689	$114.17	$114.15	$114.20
Purchase #3	$165.96	7.415%	$178.2659	$178.27	$178.25	$178.30
Purchase #4	$105.54	5.390%	$111.2286	$111.23	$111.25	$111.20
Purchase #5	$216.71	4.244%	$225.9072	$225.91	$225.90	$225.90
Purchase #6	$159.27	13.509%	$180.7858	$180.79	$180.80	$180.80
Purchase #7	$16.37	11.505%	$18.2534	$18.25	$18.25	$18.30
7 purchase totals =	$932.98		$1,010.4366	$1,010.45	$1,010.45	$1,010.50