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	$139.35	6.772%	$148.7868	$148.79	$148.80	$148.80
Purchase #2	$44.47	9.257%	$48.5866	$48.59	$48.60	$48.60
Purchase #3	$175.76	7.145%	$188.3181	$188.32	$188.30	$188.30
Purchase #4	$191.87	7.127%	$205.5446	$205.54	$205.55	$205.50
Purchase #5	$86.75	13.500%	$98.4613	$98.46	$98.45	$98.50
Purchase #6	$183.83	12.651%	$207.0863	$207.09	$207.10	$207.10
Purchase #7	$105.69	5.311%	$111.3032	$111.30	$111.30	$111.30
7 purchase totals =	$927.72		$1,008.0869	$1,008.09	$1,008.10	$1,008.10