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	$75.86	10.683%	$83.9641	$83.96	$83.95	$84.00
Purchase #2	$7.32	10.776%	$8.1088	$8.11	$8.10	$8.10
Purchase #3	$247.89	13.275%	$280.7974	$280.80	$280.80	$280.80
Purchase #4	$128.40	11.148%	$142.714	$142.71	$142.70	$142.70
Purchase #5	$100.73	4.508%	$105.2709	$105.27	$105.25	$105.30
Purchase #6	$244.28	11.381%	$272.0815	$272.08	$272.10	$272.10
Purchase #7	$192.64	6.865%	$205.8647	$205.86	$205.85	$205.90
7 purchase totals =	$997.12		$1,098.8014	$1,098.79	$1,098.75	$1,098.90