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	$74.85	10.470%	$82.6868	$82.69	$82.70	$82.70
Purchase #2	$124.63	3.158%	$128.5658	$128.57	$128.55	$128.60
Purchase #3	$197.93	13.160%	$223.9776	$223.98	$224.00	$224.00
Purchase #4	$205.85	11.811%	$230.1629	$230.16	$230.15	$230.20
Purchase #5	$181.71	9.152%	$198.3401	$198.34	$198.35	$198.30
Purchase #6	$135.46	7.102%	$145.0804	$145.08	$145.10	$145.10
Purchase #7	$173.47	8.121%	$187.5575	$187.56	$187.55	$187.60
7 purchase totals =	$1,093.90		$1,196.3711	$1,196.38	$1,196.40	$1,196.50