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	$140.80	12.805%	$158.8294	$158.83	$158.85	$158.80
Purchase #2	$213.69	6.704%	$228.0158	$228.02	$228.00	$228.00
Purchase #3	$137.36	12.712%	$154.8212	$154.82	$154.80	$154.80
Purchase #4	$73.75	6.527%	$78.5637	$78.56	$78.55	$78.60
Purchase #5	$84.82	13.577%	$96.336	$96.34	$96.35	$96.30
Purchase #6	$240.73	10.204%	$265.2941	$265.29	$265.30	$265.30
Purchase #7	$20.27	12.429%	$22.7894	$22.79	$22.80	$22.80
7 purchase totals =	$911.42		$1,004.6496	$1,004.65	$1,004.65	$1,004.60