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	$197.92	3.655%	$205.154	$205.15	$205.15	$205.20
Purchase #2	$136.77	6.596%	$145.7913	$145.79	$145.80	$145.80
Purchase #3	$148.31	4.439%	$154.8935	$154.89	$154.90	$154.90
Purchase #4	$36.89	3.378%	$38.1361	$38.14	$38.15	$38.10
Purchase #5	$104.92	10.667%	$116.1118	$116.11	$116.10	$116.10
Purchase #6	$221.90	4.322%	$231.4905	$231.49	$231.50	$231.50
Purchase #7	$175.29	11.870%	$196.0969	$196.10	$196.10	$196.10
7 purchase totals =	$1,022.00		$1,087.6741	$1,087.67	$1,087.70	$1,087.70