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	$54.55	13.762%	$62.0572	$62.06	$62.05	$62.10
Purchase #2	$152.60	13.330%	$172.9416	$172.94	$172.95	$172.90
Purchase #3	$69.39	3.237%	$71.6362	$71.64	$71.65	$71.60
Purchase #4	$31.89	5.352%	$33.5968	$33.60	$33.60	$33.60
Purchase #5	$56.60	13.429%	$64.2008	$64.20	$64.20	$64.20
Purchase #6	$188.54	5.845%	$199.5602	$199.56	$199.55	$199.60
Purchase #7	$16.41	3.232%	$16.9404	$16.94	$16.95	$16.90
7 purchase totals =	$569.98		$620.9332	$620.94	$620.95	$620.90