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	$145.28	4.850%	$152.3261	$152.33	$152.35	$152.30
Purchase #2	$58.69	7.735%	$63.2297	$63.23	$63.25	$63.20
Purchase #3	$96.49	11.732%	$107.8102	$107.81	$107.80	$107.80
Purchase #4	$114.92	11.776%	$128.453	$128.45	$128.45	$128.50
Purchase #5	$196.70	10.637%	$217.623	$217.62	$217.60	$217.60
Purchase #6	$71.44	11.664%	$79.7728	$79.77	$79.75	$79.80
Purchase #7	$95.30	5.224%	$100.2785	$100.28	$100.30	$100.30
7 purchase totals =	$778.82		$849.4933	$849.49	$849.50	$849.50