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	$197.90	12.470%	$222.5781	$222.58	$222.60	$222.60
Purchase #2	$9.62	9.295%	$10.5142	$10.51	$10.50	$10.50
Purchase #3	$37.83	6.136%	$40.1512	$40.15	$40.15	$40.20
Purchase #4	$97.87	6.401%	$104.1347	$104.13	$104.15	$104.10
Purchase #5	$62.79	12.709%	$70.77	$70.77	$70.75	$70.80
Purchase #6	$36.90	13.582%	$41.9118	$41.91	$41.90	$41.90
Purchase #7	$239.67	12.176%	$268.8522	$268.85	$268.85	$268.90
7 purchase totals =	$682.58		$758.9122	$758.90	$758.90	$759.00