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	$75.41	13.238%	$85.3928	$85.39	$85.40	$85.40
Purchase #2	$214.79	12.721%	$242.1134	$242.11	$242.10	$242.10
Purchase #3	$219.85	12.865%	$248.1337	$248.13	$248.15	$248.10
Purchase #4	$141.99	6.198%	$150.7905	$150.79	$150.80	$150.80
Purchase #5	$182.55	7.423%	$196.1007	$196.10	$196.10	$196.10
Purchase #6	$144.58	7.152%	$154.9204	$154.92	$154.90	$154.90
Purchase #7	$162.59	9.461%	$177.9726	$177.97	$177.95	$178.00
7 purchase totals =	$1,141.76		$1,255.4241	$1,255.41	$1,255.40	$1,255.40