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	$150.55	6.449%	$160.259	$160.26	$160.25	$160.30
Purchase #2	$168.88	8.583%	$183.375	$183.38	$183.40	$183.40
Purchase #3	$136.56	5.810%	$144.4941	$144.49	$144.50	$144.50
Purchase #4	$194.42	11.241%	$216.2748	$216.27	$216.25	$216.30
Purchase #5	$133.56	4.565%	$139.657	$139.66	$139.65	$139.70
Purchase #6	$210.32	5.303%	$221.4733	$221.47	$221.45	$221.50
Purchase #7	$74.95	9.264%	$81.8934	$81.89	$81.90	$81.90
7 purchase totals =	$1,069.24		$1,147.4266	$1,147.42	$1,147.40	$1,147.60