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	$148.88	3.770%	$154.4928	$154.49	$154.50	$154.50
Purchase #2	$199.46	5.712%	$210.8532	$210.85	$210.85	$210.90
Purchase #3	$202.51	9.731%	$222.2162	$222.22	$222.20	$222.20
Purchase #4	$139.32	8.479%	$151.1329	$151.13	$151.15	$151.10
Purchase #5	$197.31	9.509%	$216.0722	$216.07	$216.05	$216.10
Purchase #6	$156.55	7.354%	$168.0627	$168.06	$168.05	$168.10
Purchase #7	$214.31	12.175%	$240.4022	$240.40	$240.40	$240.40
7 purchase totals =	$1,258.34		$1,363.2322	$1,363.22	$1,363.20	$1,363.30