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	$198.60	13.820%	$226.0465	$226.05	$226.05	$226.00
Purchase #2	$222.98	7.850%	$240.4839	$240.48	$240.50	$240.50
Purchase #3	$97.44	3.119%	$100.4792	$100.48	$100.50	$100.50
Purchase #4	$11.69	10.187%	$12.8809	$12.88	$12.90	$12.90
Purchase #5	$170.49	12.745%	$192.219	$192.22	$192.20	$192.20
Purchase #6	$116.69	9.298%	$127.5398	$127.54	$127.55	$127.50
Purchase #7	$65.58	9.677%	$71.9262	$71.93	$71.95	$71.90
7 purchase totals =	$883.47		$971.5755	$971.58	$971.65	$971.50