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	$114.40	3.260%	$118.1294	$118.13	$118.15	$118.10
Purchase #2	$155.39	12.343%	$174.5698	$174.57	$174.55	$174.60
Purchase #3	$54.41	12.429%	$61.1726	$61.17	$61.15	$61.20
Purchase #4	$142.69	4.227%	$148.7215	$148.72	$148.70	$148.70
Purchase #5	$175.89	8.517%	$190.8706	$190.87	$190.85	$190.90
Purchase #6	$85.76	5.815%	$90.7469	$90.75	$90.75	$90.70
Purchase #7	$132.75	8.719%	$144.3245	$144.32	$144.30	$144.30
7 purchase totals =	$861.29		$928.5353	$928.53	$928.45	$928.50