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	$54.27	6.804%	$57.9625	$57.96	$57.95	$58.00
Purchase #2	$60.89	9.233%	$66.512	$66.51	$66.50	$66.50
Purchase #3	$38.26	12.107%	$42.8921	$42.89	$42.90	$42.90
Purchase #4	$241.87	9.572%	$265.0218	$265.02	$265.00	$265.00
Purchase #5	$83.37	7.381%	$89.5235	$89.52	$89.50	$89.50
Purchase #6	$151.84	10.167%	$167.2776	$167.28	$167.30	$167.30
Purchase #7	$45.42	5.730%	$48.0226	$48.02	$48.00	$48.00
7 purchase totals =	$675.92		$737.2121	$737.20	$737.15	$737.20