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	$137.84	4.527%	$144.08	$144.08	$144.10	$144.10
Purchase #2	$213.53	4.279%	$222.6669	$222.67	$222.65	$222.70
Purchase #3	$124.72	12.352%	$140.1254	$140.13	$140.15	$140.10
Purchase #4	$120.95	10.857%	$134.0815	$134.08	$134.10	$134.10
Purchase #5	$20.42	10.506%	$22.5653	$22.57	$22.55	$22.60
Purchase #6	$103.59	8.689%	$112.5909	$112.59	$112.60	$112.60
Purchase #7	$104.49	6.273%	$111.0447	$111.04	$111.05	$111.00
7 purchase totals =	$825.54		$887.1547	$887.16	$887.20	$887.20