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	$60.94	9.761%	$66.8884	$66.89	$66.90	$66.90
Purchase #2	$168.84	9.373%	$184.6654	$184.67	$184.65	$184.70
Purchase #3	$68.35	13.164%	$77.3476	$77.35	$77.35	$77.30
Purchase #4	$62.70	10.414%	$69.2296	$69.23	$69.25	$69.20
Purchase #5	$193.98	8.373%	$210.2219	$210.22	$210.20	$210.20
Purchase #6	$205.43	13.534%	$233.2329	$233.23	$233.25	$233.20
Purchase #7	$206.83	6.309%	$219.8789	$219.88	$219.90	$219.90
7 purchase totals =	$967.07		$1,061.4647	$1,061.47	$1,061.50	$1,061.40