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	$98.82	8.199%	$106.9223	$106.92	$106.90	$106.90
Purchase #2	$197.57	12.239%	$221.7506	$221.75	$221.75	$221.80
Purchase #3	$92.86	11.533%	$103.5695	$103.57	$103.55	$103.60
Purchase #4	$92.58	8.437%	$100.391	$100.39	$100.40	$100.40
Purchase #5	$48.67	12.341%	$54.6764	$54.68	$54.70	$54.70
Purchase #6	$53.90	10.331%	$59.4684	$59.47	$59.45	$59.50
Purchase #7	$225.62	11.854%	$252.365	$252.37	$252.35	$252.40
7 purchase totals =	$810.02		$899.1432	$899.15	$899.10	$899.30