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	$141.40	4.326%	$147.517	$147.52	$147.50	$147.50
Purchase #2	$38.55	6.178%	$40.9316	$40.93	$40.95	$40.90
Purchase #3	$229.38	9.684%	$251.5932	$251.59	$251.60	$251.60
Purchase #4	$86.52	3.312%	$89.3855	$89.39	$89.40	$89.40
Purchase #5	$82.58	10.651%	$91.3756	$91.38	$91.40	$91.40
Purchase #6	$167.67	8.170%	$181.3686	$181.37	$181.35	$181.40
Purchase #7	$55.58	12.211%	$62.3669	$62.37	$62.35	$62.40
7 purchase totals =	$801.68		$864.5384	$864.55	$864.55	$864.60