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	$128.60	10.767%	$142.4464	$142.45	$142.45	$142.40
Purchase #2	$68.98	9.282%	$75.3827	$75.38	$75.40	$75.40
Purchase #3	$130.71	11.172%	$145.3129	$145.31	$145.30	$145.30
Purchase #4	$241.59	7.565%	$259.8663	$259.87	$259.85	$259.90
Purchase #5	$189.86	3.134%	$195.8102	$195.81	$195.80	$195.80
Purchase #6	$40.62	4.136%	$42.3	$42.30	$42.30	$42.30
Purchase #7	$40.64	13.572%	$46.1557	$46.16	$46.15	$46.20
7 purchase totals =	$841.00		$907.2742	$907.28	$907.25	$907.30