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	$34.99	4.466%	$36.5527	$36.55	$36.55	$36.60
Purchase #2	$42.36	3.215%	$43.7219	$43.72	$43.70	$43.70
Purchase #3	$44.62	12.649%	$50.264	$50.26	$50.25	$50.30
Purchase #4	$76.78	9.243%	$83.8768	$83.88	$83.90	$83.90
Purchase #5	$46.80	11.403%	$52.1366	$52.14	$52.15	$52.10
Purchase #6	$17.95	10.786%	$19.8861	$19.89	$19.90	$19.90
Purchase #7	$98.78	10.739%	$109.388	$109.39	$109.40	$109.40
7 purchase totals =	$362.28		$395.8261	$395.83	$395.85	$395.90