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	$181.42	3.539%	$187.8405	$187.84	$187.85	$187.80
Purchase #2	$93.25	6.675%	$99.4744	$99.47	$99.45	$99.50
Purchase #3	$101.55	8.659%	$110.3432	$110.34	$110.35	$110.30
Purchase #4	$13.39	8.381%	$14.5122	$14.51	$14.50	$14.50
Purchase #5	$20.41	6.555%	$21.7479	$21.75	$21.75	$21.70
Purchase #6	$200.79	10.786%	$222.4472	$222.45	$222.45	$222.40
Purchase #7	$217.53	12.852%	$245.487	$245.49	$245.50	$245.50
7 purchase totals =	$828.34		$901.8524	$901.85	$901.85	$901.70