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	$164.48	8.407%	$178.3078	$178.31	$178.30	$178.30
Purchase #2	$119.65	5.392%	$126.1015	$126.10	$126.10	$126.10
Purchase #3	$67.90	3.659%	$70.3845	$70.38	$70.40	$70.40
Purchase #4	$145.80	5.397%	$153.6688	$153.67	$153.65	$153.70
Purchase #5	$166.55	11.152%	$185.1237	$185.12	$185.10	$185.10
Purchase #6	$210.61	10.585%	$232.9031	$232.90	$232.90	$232.90
Purchase #7	$54.28	5.139%	$57.0694	$57.07	$57.05	$57.10
7 purchase totals =	$929.27		$1,003.5588	$1,003.55	$1,003.50	$1,003.60