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	$240.93	3.409%	$249.1433	$249.14	$249.15	$249.10
Purchase #2	$166.30	13.416%	$188.6108	$188.61	$188.60	$188.60
Purchase #3	$214.32	11.649%	$239.2861	$239.29	$239.30	$239.30
Purchase #4	$119.38	4.230%	$124.4298	$124.43	$124.45	$124.40
Purchase #5	$59.66	13.530%	$67.732	$67.73	$67.75	$67.70
Purchase #6	$87.87	13.182%	$99.453	$99.45	$99.45	$99.50
Purchase #7	$163.71	7.130%	$175.3825	$175.38	$175.40	$175.40
7 purchase totals =	$1,052.17		$1,144.0375	$1,144.03	$1,144.10	$1,144.00