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	$61.33	11.825%	$68.5823	$68.58	$68.60	$68.60
Purchase #2	$164.70	13.843%	$187.4994	$187.50	$187.50	$187.50
Purchase #3	$100.77	10.721%	$111.5736	$111.57	$111.55	$111.60
Purchase #4	$188.84	10.853%	$209.3348	$209.33	$209.35	$209.30
Purchase #5	$16.64	9.770%	$18.2657	$18.27	$18.25	$18.30
Purchase #6	$90.73	12.106%	$101.7138	$101.71	$101.70	$101.70
Purchase #7	$64.26	7.710%	$69.2144	$69.21	$69.20	$69.20
7 purchase totals =	$687.27		$766.1840	$766.17	$766.15	$766.20