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	$53.25	7.655%	$57.3263	$57.33	$57.35	$57.30
Purchase #2	$133.80	7.859%	$144.3153	$144.32	$144.30	$144.30
Purchase #3	$240.76	6.418%	$256.212	$256.21	$256.20	$256.20
Purchase #4	$62.30	8.481%	$67.5837	$67.58	$67.60	$67.60
Purchase #5	$118.28	13.583%	$134.346	$134.35	$134.35	$134.30
Purchase #6	$148.60	12.847%	$167.6906	$167.69	$167.70	$167.70
Purchase #7	$45.73	11.699%	$51.08	$51.08	$51.10	$51.10
7 purchase totals =	$802.72		$878.5539	$878.56	$878.60	$878.50