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	$98.49	6.657%	$105.0465	$105.05	$105.05	$105.00
Purchase #2	$171.47	10.788%	$189.9682	$189.97	$189.95	$190.00
Purchase #3	$86.43	9.335%	$94.4982	$94.50	$94.50	$94.50
Purchase #4	$88.97	11.611%	$99.3003	$99.30	$99.30	$99.30
Purchase #5	$158.50	8.536%	$172.0296	$172.03	$172.05	$172.00
Purchase #6	$21.38	11.699%	$23.8812	$23.88	$23.90	$23.90
Purchase #7	$59.99	4.843%	$62.8953	$62.90	$62.90	$62.90
7 purchase totals =	$685.23		$747.6193	$747.63	$747.65	$747.60