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	$238.89	5.693%	$252.49	$252.49	$252.50	$252.50
Purchase #2	$209.48	5.689%	$221.3973	$221.40	$221.40	$221.40
Purchase #3	$151.26	11.420%	$168.5339	$168.53	$168.55	$168.50
Purchase #4	$38.77	11.730%	$43.3177	$43.32	$43.30	$43.30
Purchase #5	$219.69	10.812%	$243.4429	$243.44	$243.45	$243.40
Purchase #6	$173.97	9.710%	$190.8625	$190.86	$190.85	$190.90
Purchase #7	$80.33	13.833%	$91.442	$91.44	$91.45	$91.40
7 purchase totals =	$1,112.39		$1,211.4863	$1,211.48	$1,211.50	$1,211.40