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	$214.72	13.488%	$243.6814	$243.68	$243.70	$243.70
Purchase #2	$175.59	9.332%	$191.9761	$191.98	$192.00	$192.00
Purchase #3	$97.34	3.335%	$100.5863	$100.59	$100.60	$100.60
Purchase #4	$62.37	5.378%	$65.7243	$65.72	$65.70	$65.70
Purchase #5	$104.30	12.651%	$117.495	$117.50	$117.50	$117.50
Purchase #6	$235.60	12.486%	$265.017	$265.02	$265.00	$265.00
Purchase #7	$187.61	4.566%	$196.1763	$196.18	$196.20	$196.20
7 purchase totals =	$1,077.53		$1,180.6564	$1,180.67	$1,180.70	$1,180.70