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	$178.84	6.585%	$190.6166	$190.62	$190.60	$190.60
Purchase #2	$19.50	10.852%	$21.6161	$21.62	$21.60	$21.60
Purchase #3	$197.40	4.810%	$206.8949	$206.89	$206.90	$206.90
Purchase #4	$170.82	9.826%	$187.6048	$187.60	$187.60	$187.60
Purchase #5	$248.54	4.801%	$260.4724	$260.47	$260.45	$260.50
Purchase #6	$128.36	4.262%	$133.8307	$133.83	$133.85	$133.80
Purchase #7	$131.26	13.201%	$148.5876	$148.59	$148.60	$148.60
7 purchase totals =	$1,074.72		$1,149.6231	$1,149.62	$1,149.60	$1,149.60