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	$154.91	7.756%	$166.9248	$166.92	$166.90	$166.90
Purchase #2	$54.78	12.365%	$61.5535	$61.55	$61.55	$61.60
Purchase #3	$103.65	7.186%	$111.0983	$111.10	$111.10	$111.10
Purchase #4	$122.51	6.866%	$130.9215	$130.92	$130.90	$130.90
Purchase #5	$81.98	9.652%	$89.8927	$89.89	$89.90	$89.90
Purchase #6	$60.91	11.711%	$68.0432	$68.04	$68.05	$68.00
Purchase #7	$136.66	4.600%	$142.9464	$142.95	$142.95	$142.90
7 purchase totals =	$715.40		$771.3804	$771.37	$771.35	$771.30