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	$127.44	5.813%	$134.8481	$134.85	$134.85	$134.80
Purchase #2	$139.92	6.629%	$149.1953	$149.20	$149.20	$149.20
Purchase #3	$166.74	3.839%	$173.1411	$173.14	$173.15	$173.10
Purchase #4	$190.46	3.229%	$196.61	$196.61	$196.60	$196.60
Purchase #5	$82.59	11.609%	$92.1779	$92.18	$92.20	$92.20
Purchase #6	$52.49	12.590%	$59.0985	$59.10	$59.10	$59.10
Purchase #7	$62.94	6.103%	$66.7812	$66.78	$66.80	$66.80
7 purchase totals =	$822.58		$871.8521	$871.86	$871.90	$871.80