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	$228.32	7.279%	$244.9394	$244.94	$244.95	$244.90
Purchase #2	$171.64	5.270%	$180.6854	$180.69	$180.70	$180.70
Purchase #3	$139.47	13.619%	$158.4644	$158.46	$158.45	$158.50
Purchase #4	$120.31	7.551%	$129.3946	$129.39	$129.40	$129.40
Purchase #5	$49.76	9.536%	$54.5051	$54.51	$54.50	$54.50
Purchase #6	$76.87	12.477%	$86.4611	$86.46	$86.45	$86.50
Purchase #7	$86.42	4.389%	$90.213	$90.21	$90.20	$90.20
7 purchase totals =	$872.79		$944.6630	$944.66	$944.65	$944.70