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	$63.62	12.138%	$71.3422	$71.34	$71.35	$71.30
Purchase #2	$52.80	6.770%	$56.3746	$56.37	$56.35	$56.40
Purchase #3	$154.42	12.194%	$173.25	$173.25	$173.25	$173.30
Purchase #4	$61.42	13.684%	$69.8247	$69.82	$69.80	$69.80
Purchase #5	$220.99	4.778%	$231.5489	$231.55	$231.55	$231.50
Purchase #6	$30.32	4.186%	$31.5892	$31.59	$31.60	$31.60
Purchase #7	$73.57	6.607%	$78.4308	$78.43	$78.45	$78.40
7 purchase totals =	$657.14		$712.3604	$712.35	$712.35	$712.30