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	$128.96	9.571%	$141.3028	$141.30	$141.30	$141.30
Purchase #2	$206.92	12.813%	$233.4327	$233.43	$233.45	$233.40
Purchase #3	$118.66	7.759%	$127.8668	$127.87	$127.85	$127.90
Purchase #4	$134.28	5.154%	$141.2008	$141.20	$141.20	$141.20
Purchase #5	$117.44	4.310%	$122.5017	$122.50	$122.50	$122.50
Purchase #6	$198.46	9.136%	$216.5913	$216.59	$216.60	$216.60
Purchase #7	$55.61	8.849%	$60.5309	$60.53	$60.55	$60.50
7 purchase totals =	$960.33		$1,043.4270	$1,043.42	$1,043.45	$1,043.40