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	$163.50	5.682%	$172.7901	$172.79	$172.80	$172.80
Purchase #2	$20.86	9.396%	$22.82	$22.82	$22.80	$22.80
Purchase #3	$68.97	13.222%	$78.0892	$78.09	$78.10	$78.10
Purchase #4	$103.58	7.696%	$111.5515	$111.55	$111.55	$111.60
Purchase #5	$242.56	5.334%	$255.4982	$255.50	$255.50	$255.50
Purchase #6	$217.78	13.734%	$247.6899	$247.69	$247.70	$247.70
Purchase #7	$110.64	3.616%	$114.6407	$114.64	$114.65	$114.60
7 purchase totals =	$927.89		$1,003.0796	$1,003.08	$1,003.10	$1,003.10