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	$158.33	11.459%	$176.473	$176.47	$176.45	$176.50
Purchase #2	$79.97	13.110%	$90.4541	$90.45	$90.45	$90.50
Purchase #3	$98.64	6.774%	$105.3219	$105.32	$105.30	$105.30
Purchase #4	$132.83	10.369%	$146.6031	$146.60	$146.60	$146.60
Purchase #5	$231.94	12.498%	$260.9279	$260.93	$260.95	$260.90
Purchase #6	$195.56	5.625%	$206.5603	$206.56	$206.55	$206.60
Purchase #7	$49.97	7.398%	$53.6668	$53.67	$53.65	$53.70
7 purchase totals =	$947.24		$1,040.0071	$1,040.00	$1,039.95	$1,040.10