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	$116.53	3.480%	$120.5852	$120.59	$120.60	$120.60
Purchase #2	$18.50	9.600%	$20.276	$20.28	$20.30	$20.30
Purchase #3	$191.97	12.433%	$215.8376	$215.84	$215.85	$215.80
Purchase #4	$17.51	11.296%	$19.4879	$19.49	$19.50	$19.50
Purchase #5	$19.73	10.512%	$21.804	$21.80	$21.80	$21.80
Purchase #6	$96.55	3.362%	$99.796	$99.80	$99.80	$99.80
Purchase #7	$64.45	3.215%	$66.5221	$66.52	$66.50	$66.50
7 purchase totals =	$525.24		$564.3088	$564.32	$564.35	$564.30