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	$151.95	6.316%	$161.5472	$161.55	$161.55	$161.50
Purchase #2	$101.94	3.357%	$105.3621	$105.36	$105.35	$105.40
Purchase #3	$123.92	10.149%	$136.4966	$136.50	$136.50	$136.50
Purchase #4	$172.59	5.592%	$182.2412	$182.24	$182.25	$182.20
Purchase #5	$143.92	6.340%	$153.0445	$153.04	$153.05	$153.00
Purchase #6	$86.76	9.223%	$94.7619	$94.76	$94.75	$94.80
Purchase #7	$137.82	3.352%	$142.4397	$142.44	$142.45	$142.40
7 purchase totals =	$918.90		$975.8932	$975.89	$975.90	$975.80