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	$219.29	9.772%	$240.719	$240.72	$240.70	$240.70
Purchase #2	$52.73	6.126%	$55.9602	$55.96	$55.95	$56.00
Purchase #3	$89.95	10.528%	$99.4199	$99.42	$99.40	$99.40
Purchase #4	$200.39	9.509%	$219.4451	$219.45	$219.45	$219.40
Purchase #5	$162.36	11.580%	$181.1613	$181.16	$181.15	$181.20
Purchase #6	$93.50	12.845%	$105.5101	$105.51	$105.50	$105.50
Purchase #7	$161.60	12.577%	$181.9244	$181.92	$181.90	$181.90
7 purchase totals =	$979.82		$1,084.1400	$1,084.14	$1,084.05	$1,084.10