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	$65.81	8.455%	$71.3742	$71.37	$71.35	$71.40
Purchase #2	$118.60	4.495%	$123.9311	$123.93	$123.95	$123.90
Purchase #3	$34.93	7.144%	$37.4254	$37.43	$37.45	$37.40
Purchase #4	$88.98	8.320%	$96.3831	$96.38	$96.40	$96.40
Purchase #5	$42.67	13.173%	$48.2909	$48.29	$48.30	$48.30
Purchase #6	$208.44	13.273%	$236.1062	$236.11	$236.10	$236.10
Purchase #7	$18.80	10.306%	$20.7375	$20.74	$20.75	$20.70
7 purchase totals =	$578.23		$634.2484	$634.25	$634.30	$634.20