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	$151.95	13.800%	$172.9191	$172.92	$172.90	$172.90
Purchase #2	$115.68	6.353%	$123.0292	$123.03	$123.05	$123.00
Purchase #3	$138.31	8.332%	$149.834	$149.83	$149.85	$149.80
Purchase #4	$52.42	3.471%	$54.2395	$54.24	$54.25	$54.20
Purchase #5	$204.95	5.582%	$216.3903	$216.39	$216.40	$216.40
Purchase #6	$134.81	9.270%	$147.3069	$147.31	$147.30	$147.30
Purchase #7	$198.55	9.509%	$217.4301	$217.43	$217.45	$217.40
7 purchase totals =	$996.67		$1,081.1491	$1,081.15	$1,081.20	$1,081.00