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	$59.73	12.201%	$67.0177	$67.02	$67.00	$67.00
Purchase #2	$91.82	3.632%	$95.1549	$95.15	$95.15	$95.20
Purchase #3	$61.43	13.655%	$69.8183	$69.82	$69.80	$69.80
Purchase #4	$205.67	11.272%	$228.8531	$228.85	$228.85	$228.90
Purchase #5	$29.45	13.816%	$33.5188	$33.52	$33.50	$33.50
Purchase #6	$193.76	10.214%	$213.5506	$213.55	$213.55	$213.60
Purchase #7	$100.89	10.194%	$111.1747	$111.17	$111.15	$111.20
7 purchase totals =	$742.75		$819.0881	$819.08	$819.00	$819.20