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	$199.59	8.500%	$216.5552	$216.56	$216.55	$216.60
Purchase #2	$140.45	11.615%	$156.7633	$156.76	$156.75	$156.80
Purchase #3	$140.37	12.835%	$158.3865	$158.39	$158.40	$158.40
Purchase #4	$57.72	5.265%	$60.759	$60.76	$60.75	$60.80
Purchase #5	$101.67	9.854%	$111.6886	$111.69	$111.70	$111.70
Purchase #6	$237.87	12.128%	$266.7189	$266.72	$266.70	$266.70
Purchase #7	$186.28	13.439%	$211.3142	$211.31	$211.30	$211.30
7 purchase totals =	$1,063.95		$1,182.1857	$1,182.19	$1,182.15	$1,182.30