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	$58.60	12.518%	$65.9355	$65.94	$65.95	$65.90
Purchase #2	$138.89	8.369%	$150.5137	$150.51	$150.50	$150.50
Purchase #3	$210.67	3.270%	$217.5589	$217.56	$217.55	$217.60
Purchase #4	$146.49	12.654%	$165.0268	$165.03	$165.05	$165.00
Purchase #5	$14.36	7.591%	$15.4501	$15.45	$15.45	$15.50
Purchase #6	$237.69	4.457%	$248.2838	$248.28	$248.30	$248.30
Purchase #7	$172.90	6.608%	$184.3252	$184.33	$184.35	$184.30
7 purchase totals =	$979.60		$1,047.0940	$1,047.10	$1,047.15	$1,047.10