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	$81.32	6.136%	$86.3098	$86.31	$86.30	$86.30
Purchase #2	$191.75	8.153%	$207.3834	$207.38	$207.40	$207.40
Purchase #3	$88.94	6.555%	$94.77	$94.77	$94.75	$94.80
Purchase #4	$65.49	10.767%	$72.5413	$72.54	$72.55	$72.50
Purchase #5	$38.35	7.554%	$41.247	$41.25	$41.25	$41.20
Purchase #6	$187.91	6.856%	$200.7931	$200.79	$200.80	$200.80
Purchase #7	$38.64	8.324%	$41.8564	$41.86	$41.85	$41.90
7 purchase totals =	$692.40		$744.9010	$744.90	$744.90	$744.90