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	$58.74	10.526%	$64.923	$64.92	$64.90	$64.90
Purchase #2	$112.51	3.709%	$116.683	$116.68	$116.70	$116.70
Purchase #3	$248.42	5.307%	$261.6036	$261.60	$261.60	$261.60
Purchase #4	$133.86	7.457%	$143.8419	$143.84	$143.85	$143.80
Purchase #5	$202.29	10.556%	$223.6437	$223.64	$223.65	$223.60
Purchase #6	$94.72	10.624%	$104.7831	$104.78	$104.80	$104.80
Purchase #7	$91.73	4.566%	$95.9184	$95.92	$95.90	$95.90
7 purchase totals =	$942.27		$1,011.3967	$1,011.38	$1,011.40	$1,011.30