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	$143.89	10.343%	$158.7725	$158.77	$158.75	$158.80
Purchase #2	$22.45	12.503%	$25.2569	$25.26	$25.25	$25.30
Purchase #3	$151.71	11.453%	$169.0853	$169.09	$169.10	$169.10
Purchase #4	$163.83	10.657%	$181.2894	$181.29	$181.30	$181.30
Purchase #5	$81.71	10.861%	$90.5845	$90.58	$90.60	$90.60
Purchase #6	$149.25	6.741%	$159.3109	$159.31	$159.30	$159.30
Purchase #7	$150.29	4.203%	$156.6067	$156.61	$156.60	$156.60
7 purchase totals =	$863.13		$940.9062	$940.91	$940.90	$941.00