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	$46.87	11.304%	$52.1682	$52.17	$52.15	$52.20
Purchase #2	$38.49	11.697%	$42.9922	$42.99	$43.00	$43.00
Purchase #3	$175.99	11.612%	$196.426	$196.43	$196.45	$196.40
Purchase #4	$167.82	9.294%	$183.4172	$183.42	$183.40	$183.40
Purchase #5	$40.96	12.365%	$46.0247	$46.02	$46.00	$46.00
Purchase #6	$29.40	7.364%	$31.565	$31.57	$31.55	$31.60
Purchase #7	$45.49	8.735%	$49.4636	$49.46	$49.45	$49.50
7 purchase totals =	$545.02		$602.0569	$602.06	$602.00	$602.10