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	$142.59	10.451%	$157.4921	$157.49	$157.50	$157.50
Purchase #2	$136.72	3.205%	$141.1019	$141.10	$141.10	$141.10
Purchase #3	$218.52	12.644%	$246.1497	$246.15	$246.15	$246.10
Purchase #4	$100.94	4.797%	$105.7821	$105.78	$105.80	$105.80
Purchase #5	$109.72	9.869%	$120.5483	$120.55	$120.55	$120.50
Purchase #6	$176.50	6.781%	$188.4685	$188.47	$188.45	$188.50
Purchase #7	$219.65	9.861%	$241.3097	$241.31	$241.30	$241.30
7 purchase totals =	$1,104.64		$1,200.8523	$1,200.85	$1,200.85	$1,200.80