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	$221.88	13.438%	$251.6962	$251.70	$251.70	$251.70
Purchase #2	$132.99	11.681%	$148.5246	$148.52	$148.50	$148.50
Purchase #3	$104.97	7.238%	$112.5677	$112.57	$112.55	$112.60
Purchase #4	$99.32	12.581%	$111.8154	$111.82	$111.80	$111.80
Purchase #5	$87.90	10.311%	$96.9634	$96.96	$96.95	$97.00
Purchase #6	$91.69	4.703%	$96.0022	$96.00	$96.00	$96.00
Purchase #7	$176.92	4.618%	$185.0902	$185.09	$185.10	$185.10
7 purchase totals =	$915.67		$1,002.6597	$1,002.66	$1,002.60	$1,002.70