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	$250.90	12.530%	$282.3378	$282.34	$282.35	$282.30
Purchase #2	$196.39	9.251%	$214.558	$214.56	$214.55	$214.60
Purchase #3	$241.65	12.834%	$272.6634	$272.66	$272.65	$272.70
Purchase #4	$36.86	4.595%	$38.5537	$38.55	$38.55	$38.60
Purchase #5	$48.34	9.766%	$53.0609	$53.06	$53.05	$53.10
Purchase #6	$155.76	8.402%	$168.847	$168.85	$168.85	$168.80
Purchase #7	$180.27	6.816%	$192.5572	$192.56	$192.55	$192.60
7 purchase totals =	$1,110.17		$1,222.5780	$1,222.58	$1,222.55	$1,222.70