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	$165.75	8.354%	$179.5968	$179.60	$179.60	$179.60
Purchase #2	$193.72	9.425%	$211.9781	$211.98	$212.00	$212.00
Purchase #3	$138.81	8.638%	$150.8004	$150.80	$150.80	$150.80
Purchase #4	$103.46	12.241%	$116.1245	$116.12	$116.10	$116.10
Purchase #5	$66.42	7.777%	$71.5855	$71.59	$71.60	$71.60
Purchase #6	$160.71	3.342%	$166.0809	$166.08	$166.10	$166.10
Purchase #7	$84.47	7.562%	$90.8576	$90.86	$90.85	$90.90
7 purchase totals =	$913.34		$987.0238	$987.03	$987.05	$987.10