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	$198.42	3.543%	$205.45	$205.45	$205.45	$205.50
Purchase #2	$147.56	13.464%	$167.4275	$167.43	$167.45	$167.40
Purchase #3	$34.98	4.230%	$36.4597	$36.46	$36.45	$36.50
Purchase #4	$33.96	4.796%	$35.5887	$35.59	$35.60	$35.60
Purchase #5	$29.82	9.863%	$32.7611	$32.76	$32.75	$32.80
Purchase #6	$126.81	4.448%	$132.4505	$132.45	$132.45	$132.50
Purchase #7	$131.49	8.478%	$142.6377	$142.64	$142.65	$142.60
7 purchase totals =	$703.04		$752.7752	$752.78	$752.80	$752.90