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	$65.93	9.179%	$71.9817	$71.98	$72.00	$72.00
Purchase #2	$67.75	4.688%	$70.9261	$70.93	$70.95	$70.90
Purchase #3	$243.29	13.331%	$275.723	$275.72	$275.70	$275.70
Purchase #4	$239.57	10.453%	$264.6123	$264.61	$264.60	$264.60
Purchase #5	$19.32	11.151%	$21.4744	$21.47	$21.45	$21.50
Purchase #6	$186.57	11.239%	$207.5386	$207.54	$207.55	$207.50
Purchase #7	$181.28	3.439%	$187.5142	$187.51	$187.50	$187.50
7 purchase totals =	$1,003.71		$1,099.7703	$1,099.76	$1,099.75	$1,099.70