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	$215.59	13.840%	$245.4277	$245.43	$245.45	$245.40
Purchase #2	$103.56	5.696%	$109.4588	$109.46	$109.45	$109.50
Purchase #3	$135.82	3.463%	$140.5234	$140.52	$140.50	$140.50
Purchase #4	$148.52	5.592%	$156.8252	$156.83	$156.85	$156.80
Purchase #5	$208.37	12.330%	$234.062	$234.06	$234.05	$234.10
Purchase #6	$60.65	10.406%	$66.9612	$66.96	$66.95	$67.00
Purchase #7	$231.49	6.624%	$246.8239	$246.82	$246.80	$246.80
7 purchase totals =	$1,104.00		$1,200.0822	$1,200.08	$1,200.05	$1,200.10