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	$13.36	8.421%	$14.485	$14.49	$14.50	$14.50
Purchase #2	$132.44	9.778%	$145.39	$145.39	$145.40	$145.40
Purchase #3	$9.58	6.694%	$10.2213	$10.22	$10.20	$10.20
Purchase #4	$55.90	11.796%	$62.494	$62.49	$62.50	$62.50
Purchase #5	$22.33	12.828%	$25.1945	$25.19	$25.20	$25.20
Purchase #6	$64.96	12.231%	$72.9053	$72.91	$72.90	$72.90
Purchase #7	$177.52	10.476%	$196.117	$196.12	$196.10	$196.10
7 purchase totals =	$476.09		$526.8071	$526.81	$526.80	$526.80