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	$74.90	4.526%	$78.29	$78.29	$78.30	$78.30
Purchase #2	$249.80	13.492%	$283.503	$283.50	$283.50	$283.50
Purchase #3	$48.25	10.668%	$53.3973	$53.40	$53.40	$53.40
Purchase #4	$148.67	9.249%	$162.4205	$162.42	$162.40	$162.40
Purchase #5	$192.59	11.705%	$215.1327	$215.13	$215.15	$215.10
Purchase #6	$127.54	12.641%	$143.6623	$143.66	$143.65	$143.70
Purchase #7	$69.83	7.473%	$75.0484	$75.05	$75.05	$75.00
7 purchase totals =	$911.58		$1,011.4542	$1,011.45	$1,011.45	$1,011.40