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	$175.59	7.578%	$188.8962	$188.90	$188.90	$188.90
Purchase #2	$111.49	4.786%	$116.8259	$116.83	$116.85	$116.80
Purchase #3	$11.69	13.452%	$13.2625	$13.26	$13.25	$13.30
Purchase #4	$184.85	5.782%	$195.538	$195.54	$195.55	$195.50
Purchase #5	$234.46	10.762%	$259.6926	$259.69	$259.70	$259.70
Purchase #6	$132.53	11.305%	$147.5125	$147.51	$147.50	$147.50
Purchase #7	$103.49	7.625%	$111.3811	$111.38	$111.40	$111.40
7 purchase totals =	$954.10		$1,033.1088	$1,033.11	$1,033.15	$1,033.10