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	$49.77	10.147%	$54.8202	$54.82	$54.80	$54.80
Purchase #2	$103.40	8.232%	$111.9119	$111.91	$111.90	$111.90
Purchase #3	$99.48	10.330%	$109.7563	$109.76	$109.75	$109.80
Purchase #4	$243.77	13.387%	$276.4035	$276.40	$276.40	$276.40
Purchase #5	$97.82	12.387%	$109.937	$109.94	$109.95	$109.90
Purchase #6	$186.42	3.683%	$193.2858	$193.29	$193.30	$193.30
Purchase #7	$237.77	4.244%	$247.861	$247.86	$247.85	$247.90
7 purchase totals =	$1,018.43		$1,103.9757	$1,103.98	$1,103.95	$1,104.00