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	$127.58	5.583%	$134.7028	$134.70	$134.70	$134.70
Purchase #2	$128.63	5.713%	$135.9786	$135.98	$136.00	$136.00
Purchase #3	$47.95	9.576%	$52.5417	$52.54	$52.55	$52.50
Purchase #4	$72.77	7.782%	$78.433	$78.43	$78.45	$78.40
Purchase #5	$52.29	4.756%	$54.7769	$54.78	$54.80	$54.80
Purchase #6	$230.85	4.153%	$240.4372	$240.44	$240.45	$240.40
Purchase #7	$49.89	5.440%	$52.604	$52.60	$52.60	$52.60
7 purchase totals =	$709.96		$749.4742	$749.47	$749.55	$749.40