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	$204.61	9.371%	$223.784	$223.78	$223.80	$223.80
Purchase #2	$69.81	11.833%	$78.0706	$78.07	$78.05	$78.10
Purchase #3	$12.52	9.287%	$13.6827	$13.68	$13.70	$13.70
Purchase #4	$18.82	5.252%	$19.8084	$19.81	$19.80	$19.80
Purchase #5	$210.28	3.351%	$217.3265	$217.33	$217.35	$217.30
Purchase #6	$78.72	5.872%	$83.3424	$83.34	$83.35	$83.30
Purchase #7	$78.30	11.847%	$87.5762	$87.58	$87.60	$87.60
7 purchase totals =	$673.06		$723.5908	$723.59	$723.65	$723.60