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	$133.98	9.836%	$147.1583	$147.16	$147.15	$147.20
Purchase #2	$16.55	11.619%	$18.4729	$18.47	$18.45	$18.50
Purchase #3	$16.64	13.743%	$18.9268	$18.93	$18.95	$18.90
Purchase #4	$100.39	13.466%	$113.9085	$113.91	$113.90	$113.90
Purchase #5	$66.61	4.317%	$69.4856	$69.49	$69.50	$69.50
Purchase #6	$86.39	3.359%	$89.2918	$89.29	$89.30	$89.30
Purchase #7	$196.29	10.340%	$216.5864	$216.59	$216.60	$216.60
7 purchase totals =	$616.85		$673.8303	$673.84	$673.85	$673.90