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	$250.63	7.745%	$270.0413	$270.04	$270.05	$270.00
Purchase #2	$144.69	4.456%	$151.1374	$151.14	$151.15	$151.10
Purchase #3	$71.31	8.222%	$77.1731	$77.17	$77.15	$77.20
Purchase #4	$196.96	9.720%	$216.1045	$216.10	$216.10	$216.10
Purchase #5	$217.67	6.235%	$231.2417	$231.24	$231.25	$231.20
Purchase #6	$127.99	4.373%	$133.587	$133.59	$133.60	$133.60
Purchase #7	$56.46	9.784%	$61.984	$61.98	$62.00	$62.00
7 purchase totals =	$1,065.71		$1,141.2690	$1,141.26	$1,141.30	$1,141.20