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	$81.94	10.277%	$90.361	$90.36	$90.35	$90.40
Purchase #2	$226.83	6.346%	$241.2246	$241.22	$241.20	$241.20
Purchase #3	$191.93	12.378%	$215.6871	$215.69	$215.70	$215.70
Purchase #4	$168.40	4.817%	$176.5118	$176.51	$176.50	$176.50
Purchase #5	$143.44	11.643%	$160.1407	$160.14	$160.15	$160.10
Purchase #6	$56.99	4.705%	$59.6714	$59.67	$59.65	$59.70
Purchase #7	$71.41	13.228%	$80.8561	$80.86	$80.85	$80.90
7 purchase totals =	$940.94		$1,024.4527	$1,024.45	$1,024.40	$1,024.50