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	$116.83	5.716%	$123.508	$123.51	$123.50	$123.50
Purchase #2	$27.96	5.294%	$29.4402	$29.44	$29.45	$29.40
Purchase #3	$239.52	13.336%	$271.4624	$271.46	$271.45	$271.50
Purchase #4	$241.34	10.667%	$267.0837	$267.08	$267.10	$267.10
Purchase #5	$68.62	5.384%	$72.3145	$72.31	$72.30	$72.30
Purchase #6	$48.69	8.673%	$52.9129	$52.91	$52.90	$52.90
Purchase #7	$131.83	12.406%	$148.1848	$148.18	$148.20	$148.20
7 purchase totals =	$874.79		$964.9065	$964.89	$964.90	$964.90