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	$11.41	11.428%	$12.7139	$12.71	$12.70	$12.70
Purchase #2	$211.46	10.528%	$233.7225	$233.72	$233.70	$233.70
Purchase #3	$59.40	5.381%	$62.5963	$62.60	$62.60	$62.60
Purchase #4	$35.39	6.639%	$37.7395	$37.74	$37.75	$37.70
Purchase #5	$204.29	11.591%	$227.9693	$227.97	$227.95	$228.00
Purchase #6	$124.68	5.165%	$131.1197	$131.12	$131.10	$131.10
Purchase #7	$49.39	5.665%	$52.1879	$52.19	$52.20	$52.20
7 purchase totals =	$696.02		$758.0491	$758.05	$758.00	$758.00