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	$216.68	7.646%	$233.2474	$233.25	$233.25	$233.20
Purchase #2	$36.27	11.309%	$40.3718	$40.37	$40.35	$40.40
Purchase #3	$228.46	11.642%	$255.0573	$255.06	$255.05	$255.10
Purchase #4	$156.91	5.322%	$165.2608	$165.26	$165.25	$165.30
Purchase #5	$104.58	8.798%	$113.7809	$113.78	$113.80	$113.80
Purchase #6	$117.92	8.306%	$127.7144	$127.71	$127.70	$127.70
Purchase #7	$36.32	10.819%	$40.2495	$40.25	$40.25	$40.20
7 purchase totals =	$897.14		$975.6821	$975.68	$975.65	$975.70