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	$17.69	4.385%	$18.4657	$18.47	$18.45	$18.50
Purchase #2	$207.55	4.303%	$216.4809	$216.48	$216.50	$216.50
Purchase #3	$176.73	4.639%	$184.9285	$184.93	$184.95	$184.90
Purchase #4	$167.49	13.384%	$189.9069	$189.91	$189.90	$189.90
Purchase #5	$228.25	11.845%	$255.2862	$255.29	$255.30	$255.30
Purchase #6	$95.61	3.337%	$98.8005	$98.80	$98.80	$98.80
Purchase #7	$196.94	4.205%	$205.2213	$205.22	$205.20	$205.20
7 purchase totals =	$1,090.26		$1,169.0900	$1,169.10	$1,169.10	$1,169.10