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	$204.92	13.874%	$233.3506	$233.35	$233.35	$233.40
Purchase #2	$171.41	11.137%	$190.4999	$190.50	$190.50	$190.50
Purchase #3	$52.40	12.265%	$58.8269	$58.83	$58.85	$58.80
Purchase #4	$126.39	4.234%	$131.7414	$131.74	$131.75	$131.70
Purchase #5	$215.63	3.405%	$222.9722	$222.97	$222.95	$223.00
Purchase #6	$222.42	8.459%	$241.2345	$241.23	$241.25	$241.20
Purchase #7	$128.39	11.224%	$142.8005	$142.80	$142.80	$142.80
7 purchase totals =	$1,121.56		$1,221.4260	$1,221.42	$1,221.45	$1,221.40