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	$144.49	11.320%	$160.8463	$160.85	$160.85	$160.80
Purchase #2	$131.50	9.617%	$144.1464	$144.15	$144.15	$144.10
Purchase #3	$137.98	3.498%	$142.8065	$142.81	$142.80	$142.80
Purchase #4	$156.82	3.682%	$162.5941	$162.59	$162.60	$162.60
Purchase #5	$240.76	7.680%	$259.2504	$259.25	$259.25	$259.30
Purchase #6	$93.59	6.280%	$99.4675	$99.47	$99.45	$99.50
Purchase #7	$148.84	8.673%	$161.7489	$161.75	$161.75	$161.70
7 purchase totals =	$1,053.98		$1,130.8601	$1,130.87	$1,130.85	$1,130.80