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	$92.42	7.585%	$99.4301	$99.43	$99.45	$99.40
Purchase #2	$132.57	6.231%	$140.8304	$140.83	$140.85	$140.80
Purchase #3	$149.28	3.460%	$154.4451	$154.45	$154.45	$154.40
Purchase #4	$133.60	4.341%	$139.3996	$139.40	$139.40	$139.40
Purchase #5	$193.60	4.249%	$201.8261	$201.83	$201.85	$201.80
Purchase #6	$80.48	10.556%	$88.9755	$88.98	$89.00	$89.00
Purchase #7	$231.58	7.781%	$249.5992	$249.60	$249.60	$249.60
7 purchase totals =	$1,013.53		$1,074.5060	$1,074.52	$1,074.60	$1,074.40