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	$189.65	13.652%	$215.541	$215.54	$215.55	$215.50
Purchase #2	$63.59	13.821%	$72.3788	$72.38	$72.40	$72.40
Purchase #3	$36.65	9.822%	$40.2498	$40.25	$40.25	$40.20
Purchase #4	$236.82	3.376%	$244.815	$244.82	$244.80	$244.80
Purchase #5	$123.57	13.398%	$140.1259	$140.13	$140.15	$140.10
Purchase #6	$188.72	13.525%	$214.2444	$214.24	$214.25	$214.20
Purchase #7	$56.46	5.567%	$59.6031	$59.60	$59.60	$59.60
7 purchase totals =	$895.46		$986.9580	$986.96	$987.00	$986.80