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	$71.87	7.625%	$77.3501	$77.35	$77.35	$77.40
Purchase #2	$180.27	3.653%	$186.8553	$186.86	$186.85	$186.90
Purchase #3	$113.32	13.163%	$128.2363	$128.24	$128.25	$128.20
Purchase #4	$190.63	12.806%	$215.0421	$215.04	$215.05	$215.00
Purchase #5	$100.32	4.293%	$104.6267	$104.63	$104.65	$104.60
Purchase #6	$56.27	5.509%	$59.3699	$59.37	$59.35	$59.40
Purchase #7	$238.30	12.724%	$268.6213	$268.62	$268.60	$268.60
7 purchase totals =	$950.98		$1,040.1017	$1,040.11	$1,040.10	$1,040.10