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	$215.94	8.535%	$234.3705	$234.37	$234.35	$234.40
Purchase #2	$39.81	7.689%	$42.871	$42.87	$42.85	$42.90
Purchase #3	$196.58	12.536%	$221.2233	$221.22	$221.20	$221.20
Purchase #4	$245.25	11.842%	$274.2925	$274.29	$274.30	$274.30
Purchase #5	$41.54	10.245%	$45.7958	$45.80	$45.80	$45.80
Purchase #6	$46.45	11.433%	$51.7606	$51.76	$51.75	$51.80
Purchase #7	$54.78	5.217%	$57.6379	$57.64	$57.65	$57.60
7 purchase totals =	$840.35		$927.9516	$927.95	$927.90	$928.00