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	$9.95	12.266%	$11.1705	$11.17	$11.15	$11.20
Purchase #2	$142.41	5.397%	$150.0959	$150.10	$150.10	$150.10
Purchase #3	$121.53	12.440%	$136.6483	$136.65	$136.65	$136.60
Purchase #4	$79.82	3.304%	$82.4573	$82.46	$82.45	$82.50
Purchase #5	$127.36	9.610%	$139.5993	$139.60	$139.60	$139.60
Purchase #6	$176.52	4.435%	$184.3487	$184.35	$184.35	$184.30
Purchase #7	$196.30	5.568%	$207.23	$207.23	$207.25	$207.20
7 purchase totals =	$853.89		$911.5500	$911.56	$911.55	$911.50