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	$187.29	9.768%	$205.5845	$205.58	$205.60	$205.60
Purchase #2	$36.88	3.293%	$38.0945	$38.09	$38.10	$38.10
Purchase #3	$36.83	12.543%	$41.4496	$41.45	$41.45	$41.40
Purchase #4	$244.69	7.624%	$263.3452	$263.35	$263.35	$263.30
Purchase #5	$70.93	4.553%	$74.1594	$74.16	$74.15	$74.20
Purchase #6	$52.50	9.663%	$57.5731	$57.57	$57.55	$57.60
Purchase #7	$64.29	13.376%	$72.8894	$72.89	$72.90	$72.90
7 purchase totals =	$693.41		$753.0957	$753.09	$753.10	$753.10