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	$35.38	4.764%	$37.0655	$37.07	$37.05	$37.10
Purchase #2	$218.39	10.193%	$240.6505	$240.65	$240.65	$240.70
Purchase #3	$100.68	5.227%	$105.9425	$105.94	$105.95	$105.90
Purchase #4	$17.49	13.509%	$19.8527	$19.85	$19.85	$19.90
Purchase #5	$217.50	8.263%	$235.472	$235.47	$235.45	$235.50
Purchase #6	$181.84	7.794%	$196.0126	$196.01	$196.00	$196.00
Purchase #7	$224.88	10.467%	$248.4182	$248.42	$248.40	$248.40
7 purchase totals =	$996.16		$1,083.4140	$1,083.41	$1,083.35	$1,083.50