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	$109.85	6.651%	$117.1561	$117.16	$117.15	$117.20
Purchase #2	$242.99	6.294%	$258.2838	$258.28	$258.30	$258.30
Purchase #3	$56.90	7.277%	$61.0406	$61.04	$61.05	$61.00
Purchase #4	$139.87	13.330%	$158.5147	$158.51	$158.50	$158.50
Purchase #5	$58.67	4.302%	$61.194	$61.19	$61.20	$61.20
Purchase #6	$82.33	10.164%	$90.698	$90.70	$90.70	$90.70
Purchase #7	$10.97	7.131%	$11.7523	$11.75	$11.75	$11.80
7 purchase totals =	$701.58		$758.6395	$758.63	$758.65	$758.70