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	$112.57	13.158%	$127.382	$127.38	$127.40	$127.40
Purchase #2	$24.78	13.748%	$28.1868	$28.19	$28.20	$28.20
Purchase #3	$11.47	11.432%	$12.7813	$12.78	$12.80	$12.80
Purchase #4	$103.99	3.740%	$107.8792	$107.88	$107.90	$107.90
Purchase #5	$69.77	5.799%	$73.816	$73.82	$73.80	$73.80
Purchase #6	$203.29	9.678%	$222.9644	$222.96	$222.95	$223.00
Purchase #7	$129.85	12.805%	$146.4773	$146.48	$146.50	$146.50
7 purchase totals =	$655.72		$719.4870	$719.49	$719.55	$719.60