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	$114.64	6.332%	$121.899	$121.90	$121.90	$121.90
Purchase #2	$113.93	7.725%	$122.7311	$122.73	$122.75	$122.70
Purchase #3	$125.41	13.480%	$142.3153	$142.32	$142.30	$142.30
Purchase #4	$144.61	4.526%	$151.155	$151.16	$151.15	$151.20
Purchase #5	$238.92	7.102%	$255.8881	$255.89	$255.90	$255.90
Purchase #6	$59.32	11.668%	$66.2415	$66.24	$66.25	$66.20
Purchase #7	$173.53	8.144%	$187.6623	$187.66	$187.65	$187.70
7 purchase totals =	$970.36		$1,047.8923	$1,047.90	$1,047.90	$1,047.90