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	$220.49	3.647%	$228.5313	$228.53	$228.55	$228.50
Purchase #2	$158.61	13.183%	$179.5196	$179.52	$179.50	$179.50
Purchase #3	$9.28	11.532%	$10.3502	$10.35	$10.35	$10.40
Purchase #4	$78.48	4.457%	$81.9779	$81.98	$82.00	$82.00
Purchase #5	$127.95	10.726%	$141.6739	$141.67	$141.65	$141.70
Purchase #6	$100.61	10.686%	$111.3612	$111.36	$111.35	$111.40
Purchase #7	$161.84	12.816%	$182.5814	$182.58	$182.60	$182.60
7 purchase totals =	$857.26		$935.9955	$935.99	$936.00	$936.10