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	$165.83	10.236%	$182.8044	$182.80	$182.80	$182.80
Purchase #2	$63.59	4.218%	$66.2722	$66.27	$66.25	$66.30
Purchase #3	$201.77	3.838%	$209.5139	$209.51	$209.50	$209.50
Purchase #4	$127.80	13.294%	$144.7897	$144.79	$144.80	$144.80
Purchase #5	$197.32	4.502%	$206.2033	$206.20	$206.20	$206.20
Purchase #6	$80.36	12.265%	$90.2162	$90.22	$90.20	$90.20
Purchase #7	$137.90	11.772%	$154.1336	$154.13	$154.15	$154.10
7 purchase totals =	$974.57		$1,053.9333	$1,053.92	$1,053.90	$1,053.90