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	$207.52	8.672%	$225.5161	$225.52	$225.50	$225.50
Purchase #2	$72.65	8.661%	$78.9422	$78.94	$78.95	$78.90
Purchase #3	$157.32	11.580%	$175.5377	$175.54	$175.55	$175.50
Purchase #4	$55.28	6.133%	$58.6703	$58.67	$58.65	$58.70
Purchase #5	$222.71	4.660%	$233.0883	$233.09	$233.10	$233.10
Purchase #6	$99.50	3.693%	$103.1745	$103.17	$103.15	$103.20
Purchase #7	$121.63	7.703%	$130.9992	$131.00	$131.00	$131.00
7 purchase totals =	$936.61		$1,005.9283	$1,005.93	$1,005.90	$1,005.90