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	$233.33	10.786%	$258.497	$258.50	$258.50	$258.50
Purchase #2	$51.42	6.392%	$54.7068	$54.71	$54.70	$54.70
Purchase #3	$120.96	3.844%	$125.6097	$125.61	$125.60	$125.60
Purchase #4	$212.97	13.527%	$241.7785	$241.78	$241.80	$241.80
Purchase #5	$82.39	4.573%	$86.1577	$86.16	$86.15	$86.20
Purchase #6	$187.95	11.517%	$209.5962	$209.60	$209.60	$209.60
Purchase #7	$88.43	13.125%	$100.0364	$100.04	$100.05	$100.00
7 purchase totals =	$977.45		$1,076.3823	$1,076.40	$1,076.40	$1,076.40