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	$207.89	7.775%	$224.0534	$224.05	$224.05	$224.10
Purchase #2	$98.37	13.169%	$111.3243	$111.32	$111.30	$111.30
Purchase #3	$56.62	10.460%	$62.5425	$62.54	$62.55	$62.50
Purchase #4	$233.70	11.436%	$260.4259	$260.43	$260.45	$260.40
Purchase #5	$228.89	11.195%	$254.5142	$254.51	$254.50	$254.50
Purchase #6	$13.38	10.141%	$14.7369	$14.74	$14.75	$14.70
Purchase #7	$90.56	5.730%	$95.7491	$95.75	$95.75	$95.70
7 purchase totals =	$929.41		$1,023.3463	$1,023.34	$1,023.35	$1,023.20