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	$43.88	3.471%	$45.4031	$45.40	$45.40	$45.40
Purchase #2	$46.78	13.151%	$52.932	$52.93	$52.95	$52.90
Purchase #3	$135.85	13.308%	$153.9289	$153.93	$153.95	$153.90
Purchase #4	$159.40	11.417%	$177.5987	$177.60	$177.60	$177.60
Purchase #5	$241.39	5.802%	$255.3954	$255.40	$255.40	$255.40
Purchase #6	$124.69	4.104%	$129.8073	$129.81	$129.80	$129.80
Purchase #7	$105.50	4.789%	$110.5524	$110.55	$110.55	$110.60
7 purchase totals =	$857.49		$925.6178	$925.62	$925.65	$925.60