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	$132.89	9.662%	$145.7298	$145.73	$145.75	$145.70
Purchase #2	$67.87	3.710%	$70.388	$70.39	$70.40	$70.40
Purchase #3	$56.71	4.648%	$59.3459	$59.35	$59.35	$59.30
Purchase #4	$34.53	3.677%	$35.7997	$35.80	$35.80	$35.80
Purchase #5	$17.98	12.699%	$20.2633	$20.26	$20.25	$20.30
Purchase #6	$47.41	11.728%	$52.9702	$52.97	$52.95	$53.00
Purchase #7	$196.83	4.691%	$206.0633	$206.06	$206.05	$206.10
7 purchase totals =	$554.22		$590.5602	$590.56	$590.55	$590.60