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	$132.37	7.873%	$142.7915	$142.79	$142.80	$142.80
Purchase #2	$82.26	8.232%	$89.0316	$89.03	$89.05	$89.00
Purchase #3	$178.56	12.524%	$200.9229	$200.92	$200.90	$200.90
Purchase #4	$214.81	7.139%	$230.1453	$230.15	$230.15	$230.10
Purchase #5	$136.97	3.280%	$141.4626	$141.46	$141.45	$141.50
Purchase #6	$152.25	10.602%	$168.3915	$168.39	$168.40	$168.40
Purchase #7	$54.93	3.671%	$56.9465	$56.95	$56.95	$56.90
7 purchase totals =	$952.15		$1,029.6919	$1,029.69	$1,029.70	$1,029.60