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	$22.36	6.242%	$23.7557	$23.76	$23.75	$23.80
Purchase #2	$182.98	7.159%	$196.0795	$196.08	$196.10	$196.10
Purchase #3	$42.87	5.698%	$45.3127	$45.31	$45.30	$45.30
Purchase #4	$177.89	3.642%	$184.3688	$184.37	$184.35	$184.40
Purchase #5	$223.57	10.751%	$247.606	$247.61	$247.60	$247.60
Purchase #6	$106.27	10.194%	$117.1032	$117.10	$117.10	$117.10
Purchase #7	$19.62	7.791%	$21.1486	$21.15	$21.15	$21.10
7 purchase totals =	$775.56		$835.3745	$835.38	$835.35	$835.40