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	$178.73	9.817%	$196.2759	$196.28	$196.30	$196.30
Purchase #2	$123.92	8.504%	$134.4582	$134.46	$134.45	$134.50
Purchase #3	$20.79	4.513%	$21.7283	$21.73	$21.75	$21.70
Purchase #4	$218.96	5.437%	$230.8649	$230.86	$230.85	$230.90
Purchase #5	$232.55	7.687%	$250.4261	$250.43	$250.45	$250.40
Purchase #6	$38.39	13.421%	$43.5423	$43.54	$43.55	$43.50
Purchase #7	$13.58	10.330%	$14.9828	$14.98	$15.00	$15.00
7 purchase totals =	$826.92		$892.2785	$892.28	$892.35	$892.30