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	$146.58	5.754%	$155.0142	$155.01	$155.00	$155.00
Purchase #2	$32.42	13.813%	$36.8982	$36.90	$36.90	$36.90
Purchase #3	$52.34	9.491%	$57.3076	$57.31	$57.30	$57.30
Purchase #4	$16.50	9.120%	$18.0048	$18.00	$18.00	$18.00
Purchase #5	$111.25	3.242%	$114.8567	$114.86	$114.85	$114.90
Purchase #6	$144.77	12.423%	$162.7548	$162.75	$162.75	$162.80
Purchase #7	$122.69	8.801%	$133.4879	$133.49	$133.50	$133.50
7 purchase totals =	$626.55		$678.3242	$678.32	$678.30	$678.40