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	$109.92	12.194%	$123.3236	$123.32	$123.30	$123.30
Purchase #2	$119.70	10.798%	$132.6252	$132.63	$132.65	$132.60
Purchase #3	$103.92	5.685%	$109.8279	$109.83	$109.85	$109.80
Purchase #4	$202.88	10.508%	$224.1986	$224.20	$224.20	$224.20
Purchase #5	$95.30	4.519%	$99.6066	$99.61	$99.60	$99.60
Purchase #6	$151.65	8.779%	$164.9634	$164.96	$164.95	$165.00
Purchase #7	$235.94	5.732%	$249.4641	$249.46	$249.45	$249.50
7 purchase totals =	$1,019.31		$1,104.0094	$1,104.01	$1,104.00	$1,104.00