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	$228.46	6.565%	$243.4584	$243.46	$243.45	$243.50
Purchase #2	$81.50	13.382%	$92.4063	$92.41	$92.40	$92.40
Purchase #3	$150.93	5.323%	$158.964	$158.96	$158.95	$159.00
Purchase #4	$95.43	3.840%	$99.0945	$99.09	$99.10	$99.10
Purchase #5	$104.36	4.321%	$108.8694	$108.87	$108.85	$108.90
Purchase #6	$184.30	3.489%	$190.7302	$190.73	$190.75	$190.70
Purchase #7	$67.83	3.708%	$70.3451	$70.35	$70.35	$70.30
7 purchase totals =	$912.81		$963.8679	$963.87	$963.85	$963.90