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	$161.53	12.656%	$181.9732	$181.97	$181.95	$182.00
Purchase #2	$179.27	9.845%	$196.9191	$196.92	$196.90	$196.90
Purchase #3	$114.68	8.242%	$124.1319	$124.13	$124.15	$124.10
Purchase #4	$49.48	5.426%	$52.1648	$52.16	$52.15	$52.20
Purchase #5	$112.70	9.692%	$123.6229	$123.62	$123.60	$123.60
Purchase #6	$194.59	10.414%	$214.8546	$214.85	$214.85	$214.90
Purchase #7	$190.45	4.111%	$198.2794	$198.28	$198.30	$198.30
7 purchase totals =	$1,002.70		$1,091.9459	$1,091.93	$1,091.90	$1,092.00