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	$113.42	3.385%	$117.2593	$117.26	$117.25	$117.30
Purchase #2	$140.44	3.476%	$145.3217	$145.32	$145.30	$145.30
Purchase #3	$46.29	13.809%	$52.6822	$52.68	$52.70	$52.70
Purchase #4	$193.83	7.703%	$208.7607	$208.76	$208.75	$208.80
Purchase #5	$99.72	11.827%	$111.5139	$111.51	$111.50	$111.50
Purchase #6	$56.42	5.411%	$59.4729	$59.47	$59.45	$59.50
Purchase #7	$85.61	11.442%	$95.4055	$95.41	$95.40	$95.40
7 purchase totals =	$735.73		$790.4162	$790.41	$790.35	$790.50