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	$152.69	10.373%	$168.5285	$168.53	$168.55	$168.50
Purchase #2	$220.36	13.828%	$250.8314	$250.83	$250.85	$250.80
Purchase #3	$78.47	5.277%	$82.6109	$82.61	$82.60	$82.60
Purchase #4	$166.63	9.181%	$181.9283	$181.93	$181.95	$181.90
Purchase #5	$50.91	6.455%	$54.1962	$54.20	$54.20	$54.20
Purchase #6	$195.95	6.273%	$208.2419	$208.24	$208.25	$208.20
Purchase #7	$119.76	11.293%	$133.2845	$133.28	$133.30	$133.30
7 purchase totals =	$984.77		$1,079.6217	$1,079.62	$1,079.70	$1,079.50