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	$241.27	5.717%	$255.0634	$255.06	$255.05	$255.10
Purchase #2	$114.27	11.166%	$127.0294	$127.03	$127.05	$127.00
Purchase #3	$123.77	3.401%	$127.9794	$127.98	$128.00	$128.00
Purchase #4	$204.40	8.744%	$222.2727	$222.27	$222.25	$222.30
Purchase #5	$112.86	9.530%	$123.6156	$123.62	$123.60	$123.60
Purchase #6	$156.83	5.857%	$166.0155	$166.02	$166.00	$166.00
Purchase #7	$146.40	6.270%	$155.5793	$155.58	$155.60	$155.60
7 purchase totals =	$1,099.80		$1,177.5553	$1,177.56	$1,177.55	$1,177.60