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	$196.93	4.776%	$206.3354	$206.34	$206.35	$206.30
Purchase #2	$42.26	13.368%	$47.9093	$47.91	$47.90	$47.90
Purchase #3	$62.79	6.575%	$66.9184	$66.92	$66.90	$66.90
Purchase #4	$242.97	6.251%	$258.1581	$258.16	$258.15	$258.20
Purchase #5	$100.85	6.552%	$107.4577	$107.46	$107.45	$107.50
Purchase #6	$30.65	6.356%	$32.5981	$32.60	$32.60	$32.60
Purchase #7	$62.32	7.658%	$67.0925	$67.09	$67.10	$67.10
7 purchase totals =	$738.77		$786.4695	$786.48	$786.45	$786.50