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	$59.60	4.506%	$62.2856	$62.29	$62.30	$62.30
Purchase #2	$140.33	3.402%	$145.104	$145.10	$145.10	$145.10
Purchase #3	$142.77	12.669%	$160.8575	$160.86	$160.85	$160.90
Purchase #4	$219.60	7.243%	$235.5056	$235.51	$235.50	$235.50
Purchase #5	$15.74	11.418%	$17.5372	$17.54	$17.55	$17.50
Purchase #6	$114.99	10.111%	$126.6166	$126.62	$126.60	$126.60
Purchase #7	$117.54	8.239%	$127.2241	$127.22	$127.20	$127.20
7 purchase totals =	$810.57		$875.1306	$875.14	$875.10	$875.10