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	$233.27	3.550%	$241.5511	$241.55	$241.55	$241.60
Purchase #2	$209.52	7.159%	$224.5195	$224.52	$224.50	$224.50
Purchase #3	$62.63	4.700%	$65.5736	$65.57	$65.55	$65.60
Purchase #4	$43.95	12.452%	$49.4227	$49.42	$49.40	$49.40
Purchase #5	$118.67	8.433%	$128.6774	$128.68	$128.70	$128.70
Purchase #6	$121.31	5.155%	$127.5635	$127.56	$127.55	$127.60
Purchase #7	$132.99	4.834%	$139.4187	$139.42	$139.40	$139.40
7 purchase totals =	$922.34		$976.7265	$976.72	$976.65	$976.80