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	$196.56	10.600%	$217.3954	$217.40	$217.40	$217.40
Purchase #2	$127.67	12.851%	$144.0769	$144.08	$144.10	$144.10
Purchase #3	$193.60	6.674%	$206.5209	$206.52	$206.50	$206.50
Purchase #4	$14.28	9.266%	$15.6032	$15.60	$15.60	$15.60
Purchase #5	$18.71	6.140%	$19.8588	$19.86	$19.85	$19.90
Purchase #6	$114.92	3.432%	$118.8641	$118.86	$118.85	$118.90
Purchase #7	$61.69	7.815%	$66.5111	$66.51	$66.50	$66.50
7 purchase totals =	$727.43		$788.8304	$788.83	$788.80	$788.90