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	$159.40	9.671%	$174.8156	$174.82	$174.80	$174.80
Purchase #2	$111.51	6.850%	$119.1484	$119.15	$119.15	$119.10
Purchase #3	$94.49	6.133%	$100.2851	$100.29	$100.30	$100.30
Purchase #4	$37.64	5.460%	$39.6951	$39.70	$39.70	$39.70
Purchase #5	$39.50	13.541%	$44.8487	$44.85	$44.85	$44.80
Purchase #6	$59.82	7.429%	$64.264	$64.26	$64.25	$64.30
Purchase #7	$162.90	9.534%	$178.4309	$178.43	$178.45	$178.40
7 purchase totals =	$665.26		$721.4878	$721.50	$721.50	$721.40