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	$197.52	5.492%	$208.3678	$208.37	$208.35	$208.40
Purchase #2	$140.46	13.140%	$158.9164	$158.92	$158.90	$158.90
Purchase #3	$39.47	5.807%	$41.762	$41.76	$41.75	$41.80
Purchase #4	$207.33	11.310%	$230.779	$230.78	$230.80	$230.80
Purchase #5	$90.93	3.543%	$94.1516	$94.15	$94.15	$94.20
Purchase #6	$198.82	3.231%	$205.2439	$205.24	$205.25	$205.20
Purchase #7	$82.51	12.171%	$92.5523	$92.55	$92.55	$92.60
7 purchase totals =	$957.04		$1,031.7730	$1,031.77	$1,031.75	$1,031.90