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	$40.26	7.528%	$43.2908	$43.29	$43.30	$43.30
Purchase #2	$156.88	7.332%	$168.3824	$168.38	$168.40	$168.40
Purchase #3	$59.49	10.646%	$65.8233	$65.82	$65.80	$65.80
Purchase #4	$61.98	5.866%	$65.6157	$65.62	$65.60	$65.60
Purchase #5	$158.81	3.410%	$164.2254	$164.23	$164.25	$164.20
Purchase #6	$208.62	10.308%	$230.1245	$230.12	$230.10	$230.10
Purchase #7	$243.73	12.443%	$274.0573	$274.06	$274.05	$274.10
7 purchase totals =	$929.77		$1,011.5194	$1,011.52	$1,011.50	$1,011.50