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	$124.67	6.688%	$133.0079	$133.01	$133.00	$133.00
Purchase #2	$173.56	6.508%	$184.8553	$184.86	$184.85	$184.90
Purchase #3	$149.28	4.283%	$155.6737	$155.67	$155.65	$155.70
Purchase #4	$50.63	7.371%	$54.3619	$54.36	$54.35	$54.40
Purchase #5	$215.84	5.286%	$227.2493	$227.25	$227.25	$227.20
Purchase #6	$111.94	10.250%	$123.4139	$123.41	$123.40	$123.40
Purchase #7	$81.65	9.127%	$89.1022	$89.10	$89.10	$89.10
7 purchase totals =	$907.57		$967.6642	$967.66	$967.60	$967.70