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	$158.93	8.482%	$172.4104	$172.41	$172.40	$172.40
Purchase #2	$46.39	12.853%	$52.3525	$52.35	$52.35	$52.40
Purchase #3	$47.28	5.468%	$49.8653	$49.87	$49.85	$49.90
Purchase #4	$142.79	8.374%	$154.7472	$154.75	$154.75	$154.70
Purchase #5	$160.52	5.454%	$169.2748	$169.27	$169.25	$169.30
Purchase #6	$211.90	4.669%	$221.7936	$221.79	$221.80	$221.80
Purchase #7	$100.66	10.689%	$111.4195	$111.42	$111.40	$111.40
7 purchase totals =	$868.47		$931.8633	$931.86	$931.80	$931.90