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	$37.38	3.392%	$38.6479	$38.65	$38.65	$38.60
Purchase #2	$158.48	6.369%	$168.5736	$168.57	$168.55	$168.60
Purchase #3	$145.81	4.592%	$152.5056	$152.51	$152.50	$152.50
Purchase #4	$203.48	6.716%	$217.1457	$217.15	$217.15	$217.10
Purchase #5	$224.65	7.400%	$241.2741	$241.27	$241.25	$241.30
Purchase #6	$66.59	7.155%	$71.3545	$71.35	$71.35	$71.40
Purchase #7	$74.88	9.647%	$82.1037	$82.10	$82.10	$82.10
7 purchase totals =	$911.27		$971.6051	$971.60	$971.55	$971.60