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	$153.30	5.393%	$161.5675	$161.57	$161.55	$161.60
Purchase #2	$185.82	7.357%	$199.4908	$199.49	$199.50	$199.50
Purchase #3	$188.56	13.710%	$214.4116	$214.41	$214.40	$214.40
Purchase #4	$99.28	9.837%	$109.0462	$109.05	$109.05	$109.00
Purchase #5	$205.86	9.549%	$225.5176	$225.52	$225.50	$225.50
Purchase #6	$152.67	13.649%	$173.5079	$173.51	$173.50	$173.50
Purchase #7	$12.73	4.486%	$13.3011	$13.30	$13.30	$13.30
7 purchase totals =	$998.22		$1,096.8427	$1,096.85	$1,096.80	$1,096.80