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	$127.80	13.683%	$145.2869	$145.29	$145.30	$145.30
Purchase #2	$26.71	5.402%	$28.1529	$28.15	$28.15	$28.20
Purchase #3	$54.29	5.856%	$57.4692	$57.47	$57.45	$57.50
Purchase #4	$75.47	13.165%	$85.4056	$85.41	$85.40	$85.40
Purchase #5	$224.74	10.587%	$248.5332	$248.53	$248.55	$248.50
Purchase #6	$228.80	12.254%	$256.8372	$256.84	$256.85	$256.80
Purchase #7	$229.27	5.773%	$242.5058	$242.51	$242.50	$242.50
7 purchase totals =	$967.08		$1,064.1908	$1,064.20	$1,064.20	$1,064.20