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	$59.69	6.261%	$63.4272	$63.43	$63.45	$63.40
Purchase #2	$176.46	6.679%	$188.2458	$188.25	$188.25	$188.20
Purchase #3	$85.64	8.379%	$92.8158	$92.82	$92.80	$92.80
Purchase #4	$233.61	11.269%	$259.9355	$259.94	$259.95	$259.90
Purchase #5	$10.52	7.590%	$11.3185	$11.32	$11.30	$11.30
Purchase #6	$179.85	4.762%	$188.4145	$188.41	$188.40	$188.40
Purchase #7	$110.37	12.835%	$124.536	$124.54	$124.55	$124.50
7 purchase totals =	$856.14		$928.6933	$928.71	$928.70	$928.50