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	$82.66	8.398%	$89.6018	$89.60	$89.60	$89.60
Purchase #2	$128.31	10.389%	$141.6401	$141.64	$141.65	$141.60
Purchase #3	$164.68	8.753%	$179.0944	$179.09	$179.10	$179.10
Purchase #4	$228.34	4.147%	$237.8093	$237.81	$237.80	$237.80
Purchase #5	$50.40	9.431%	$55.1532	$55.15	$55.15	$55.20
Purchase #6	$154.78	4.679%	$162.0222	$162.02	$162.00	$162.00
Purchase #7	$157.98	6.659%	$168.4999	$168.50	$168.50	$168.50
7 purchase totals =	$967.15		$1,033.8209	$1,033.81	$1,033.80	$1,033.80