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	$151.64	3.484%	$156.9231	$156.92	$156.90	$156.90
Purchase #2	$127.25	3.623%	$131.8603	$131.86	$131.85	$131.90
Purchase #3	$72.28	12.174%	$81.0794	$81.08	$81.10	$81.10
Purchase #4	$216.64	13.792%	$246.519	$246.52	$246.50	$246.50
Purchase #5	$11.75	7.583%	$12.641	$12.64	$12.65	$12.60
Purchase #6	$80.37	13.483%	$91.2063	$91.21	$91.20	$91.20
Purchase #7	$51.34	6.647%	$54.7526	$54.75	$54.75	$54.80
7 purchase totals =	$711.27		$774.9817	$774.98	$774.95	$775.00