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	$177.65	8.813%	$193.3063	$193.31	$193.30	$193.30
Purchase #2	$201.85	10.214%	$222.467	$222.47	$222.45	$222.50
Purchase #3	$115.43	10.594%	$127.6587	$127.66	$127.65	$127.70
Purchase #4	$58.72	10.849%	$65.0905	$65.09	$65.10	$65.10
Purchase #5	$198.28	12.185%	$222.4404	$222.44	$222.45	$222.40
Purchase #6	$209.27	5.568%	$220.9222	$220.92	$220.90	$220.90
Purchase #7	$233.87	12.403%	$262.8769	$262.88	$262.90	$262.90
7 purchase totals =	$1,195.07		$1,314.7620	$1,314.77	$1,314.75	$1,314.80