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	$144.73	13.493%	$164.2584	$164.26	$164.25	$164.30
Purchase #2	$145.88	3.644%	$151.1959	$151.20	$151.20	$151.20
Purchase #3	$81.88	10.199%	$90.2309	$90.23	$90.25	$90.20
Purchase #4	$108.62	8.340%	$117.6789	$117.68	$117.70	$117.70
Purchase #5	$82.85	12.113%	$92.8856	$92.89	$92.90	$92.90
Purchase #6	$148.41	5.183%	$156.1021	$156.10	$156.10	$156.10
Purchase #7	$228.31	6.537%	$243.2346	$243.23	$243.25	$243.20
7 purchase totals =	$940.68		$1,015.5864	$1,015.59	$1,015.65	$1,015.60