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	$206.72	10.833%	$229.114	$229.11	$229.10	$229.10
Purchase #2	$62.26	5.181%	$65.4857	$65.49	$65.50	$65.50
Purchase #3	$216.79	13.256%	$245.5277	$245.53	$245.55	$245.50
Purchase #4	$80.29	12.396%	$90.2427	$90.24	$90.25	$90.20
Purchase #5	$181.25	4.109%	$188.6976	$188.70	$188.70	$188.70
Purchase #6	$214.88	11.426%	$239.4322	$239.43	$239.45	$239.40
Purchase #7	$142.26	6.789%	$151.918	$151.92	$151.90	$151.90
7 purchase totals =	$1,104.45		$1,210.4179	$1,210.42	$1,210.45	$1,210.30