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	$229.77	7.396%	$246.7638	$246.76	$246.75	$246.80
Purchase #2	$94.29	5.487%	$99.4637	$99.46	$99.45	$99.50
Purchase #3	$219.98	8.622%	$238.9467	$238.95	$238.95	$238.90
Purchase #4	$70.34	11.193%	$78.2132	$78.21	$78.20	$78.20
Purchase #5	$27.79	9.293%	$30.3725	$30.37	$30.35	$30.40
Purchase #6	$172.85	8.333%	$187.2536	$187.25	$187.25	$187.30
Purchase #7	$154.46	12.274%	$173.4184	$173.42	$173.40	$173.40
7 purchase totals =	$969.48		$1,054.4319	$1,054.42	$1,054.35	$1,054.50