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	$212.37	5.658%	$224.3859	$224.39	$224.40	$224.40
Purchase #2	$151.94	13.231%	$172.0432	$172.04	$172.05	$172.00
Purchase #3	$49.59	12.115%	$55.5978	$55.60	$55.60	$55.60
Purchase #4	$35.78	4.196%	$37.2813	$37.28	$37.30	$37.30
Purchase #5	$241.68	7.364%	$259.4773	$259.48	$259.50	$259.50
Purchase #6	$188.62	6.377%	$200.6483	$200.65	$200.65	$200.60
Purchase #7	$140.69	13.747%	$160.0307	$160.03	$160.05	$160.00
7 purchase totals =	$1,020.67		$1,109.4645	$1,109.47	$1,109.55	$1,109.40