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	$223.83	7.735%	$241.1433	$241.14	$241.15	$241.10
Purchase #2	$67.79	7.604%	$72.9448	$72.94	$72.95	$72.90
Purchase #3	$192.70	6.661%	$205.5357	$205.54	$205.55	$205.50
Purchase #4	$119.66	3.227%	$123.5214	$123.52	$123.50	$123.50
Purchase #5	$115.48	9.246%	$126.1573	$126.16	$126.15	$126.20
Purchase #6	$133.48	7.457%	$143.4336	$143.43	$143.45	$143.40
Purchase #7	$16.32	3.400%	$16.8749	$16.87	$16.85	$16.90
7 purchase totals =	$869.26		$929.6110	$929.60	$929.60	$929.50