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	$205.96	5.714%	$217.7286	$217.73	$217.75	$217.70
Purchase #2	$66.42	6.167%	$70.5161	$70.52	$70.50	$70.50
Purchase #3	$5.84	12.157%	$6.55	$6.55	$6.55	$6.60
Purchase #4	$160.43	4.635%	$167.8659	$167.87	$167.85	$167.90
Purchase #5	$35.83	12.630%	$40.3553	$40.36	$40.35	$40.40
Purchase #6	$50.52	9.859%	$55.5008	$55.50	$55.50	$55.50
Purchase #7	$64.60	13.644%	$73.414	$73.41	$73.40	$73.40
7 purchase totals =	$589.60		$631.9307	$631.94	$631.90	$632.00