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	$44.75	12.541%	$50.3621	$50.36	$50.35	$50.40
Purchase #2	$153.56	4.669%	$160.7297	$160.73	$160.75	$160.70
Purchase #3	$9.54	8.741%	$10.3739	$10.37	$10.35	$10.40
Purchase #4	$150.64	10.463%	$166.4015	$166.40	$166.40	$166.40
Purchase #5	$190.28	3.380%	$196.7115	$196.71	$196.70	$196.70
Purchase #6	$151.52	3.136%	$156.2717	$156.27	$156.25	$156.30
Purchase #7	$248.82	4.827%	$260.8305	$260.83	$260.85	$260.80
7 purchase totals =	$949.11		$1,001.6809	$1,001.67	$1,001.65	$1,001.70