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	$81.98	11.433%	$91.3528	$91.35	$91.35	$91.40
Purchase #2	$142.89	12.659%	$160.9784	$160.98	$161.00	$161.00
Purchase #3	$73.68	6.620%	$78.5576	$78.56	$78.55	$78.60
Purchase #4	$204.82	12.283%	$229.978	$229.98	$230.00	$230.00
Purchase #5	$112.77	4.245%	$117.5571	$117.56	$117.55	$117.60
Purchase #6	$154.95	13.351%	$175.6374	$175.64	$175.65	$175.60
Purchase #7	$131.97	11.261%	$146.8311	$146.83	$146.85	$146.80
7 purchase totals =	$903.06		$1,000.8924	$1,000.90	$1,000.95	$1,001.00