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	$44.30	4.313%	$46.2107	$46.21	$46.20	$46.20
Purchase #2	$31.82	11.374%	$35.4392	$35.44	$35.45	$35.40
Purchase #3	$131.89	9.140%	$143.9447	$143.94	$143.95	$143.90
Purchase #4	$60.46	3.772%	$62.7406	$62.74	$62.75	$62.70
Purchase #5	$24.26	5.229%	$25.5286	$25.53	$25.55	$25.50
Purchase #6	$128.38	11.514%	$143.1617	$143.16	$143.15	$143.20
Purchase #7	$99.78	8.530%	$108.2912	$108.29	$108.30	$108.30
7 purchase totals =	$520.89		$565.3167	$565.31	$565.35	$565.20