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	$66.73	8.393%	$72.3306	$72.33	$72.35	$72.30
Purchase #2	$78.61	11.146%	$87.3719	$87.37	$87.35	$87.40
Purchase #3	$32.37	4.855%	$33.9416	$33.94	$33.95	$33.90
Purchase #4	$178.74	4.633%	$187.021	$187.02	$187.00	$187.00
Purchase #5	$126.35	5.631%	$133.4648	$133.46	$133.45	$133.50
Purchase #6	$10.77	7.490%	$11.5767	$11.58	$11.60	$11.60
Purchase #7	$162.72	6.136%	$172.7045	$172.70	$172.70	$172.70
7 purchase totals =	$656.29		$698.4111	$698.40	$698.40	$698.40