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	$106.31	5.208%	$111.8466	$111.85	$111.85	$111.80
Purchase #2	$201.45	5.111%	$211.7461	$211.75	$211.75	$211.70
Purchase #3	$180.70	10.578%	$199.8144	$199.81	$199.80	$199.80
Purchase #4	$119.85	12.436%	$134.7545	$134.75	$134.75	$134.80
Purchase #5	$148.35	13.127%	$167.8239	$167.82	$167.80	$167.80
Purchase #6	$82.67	4.394%	$86.3025	$86.30	$86.30	$86.30
Purchase #7	$234.94	4.708%	$246.001	$246.00	$246.00	$246.00
7 purchase totals =	$1,074.27		$1,158.2890	$1,158.28	$1,158.25	$1,158.20