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	$44.40	10.722%	$49.1606	$49.16	$49.15	$49.20
Purchase #2	$161.72	11.626%	$180.5216	$180.52	$180.50	$180.50
Purchase #3	$61.78	12.447%	$69.4698	$69.47	$69.45	$69.50
Purchase #4	$6.43	12.644%	$7.243	$7.24	$7.25	$7.20
Purchase #5	$105.44	13.468%	$119.6407	$119.64	$119.65	$119.60
Purchase #6	$210.39	13.487%	$238.7653	$238.77	$238.75	$238.80
Purchase #7	$85.90	4.376%	$89.659	$89.66	$89.65	$89.70
7 purchase totals =	$676.06		$754.4600	$754.46	$754.40	$754.50