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	$64.46	6.325%	$68.5371	$68.54	$68.55	$68.50
Purchase #2	$62.28	7.194%	$66.7604	$66.76	$66.75	$66.80
Purchase #3	$167.82	5.317%	$176.743	$176.74	$176.75	$176.70
Purchase #4	$121.83	4.249%	$127.0066	$127.01	$127.00	$127.00
Purchase #5	$211.88	6.532%	$225.72	$225.72	$225.70	$225.70
Purchase #6	$220.27	6.859%	$235.3783	$235.38	$235.40	$235.40
Purchase #7	$112.46	4.772%	$117.8266	$117.83	$117.85	$117.80
7 purchase totals =	$961.00		$1,017.9720	$1,017.98	$1,018.00	$1,017.90