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	$167.80	5.415%	$176.8864	$176.89	$176.90	$176.90
Purchase #2	$69.48	11.552%	$77.5063	$77.51	$77.50	$77.50
Purchase #3	$155.97	12.511%	$175.4834	$175.48	$175.50	$175.50
Purchase #4	$86.82	5.124%	$91.2687	$91.27	$91.25	$91.30
Purchase #5	$121.77	10.133%	$134.109	$134.11	$134.10	$134.10
Purchase #6	$248.78	12.778%	$280.5691	$280.57	$280.55	$280.60
Purchase #7	$137.45	11.164%	$152.7949	$152.79	$152.80	$152.80
7 purchase totals =	$988.07		$1,088.6178	$1,088.62	$1,088.60	$1,088.70