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	$115.54	10.298%	$127.4383	$127.44	$127.45	$127.40
Purchase #2	$10.33	10.319%	$11.396	$11.40	$11.40	$11.40
Purchase #3	$222.55	11.384%	$247.8851	$247.89	$247.90	$247.90
Purchase #4	$18.74	6.351%	$19.9302	$19.93	$19.95	$19.90
Purchase #5	$52.34	4.754%	$54.8282	$54.83	$54.85	$54.80
Purchase #6	$55.60	9.725%	$61.0071	$61.01	$61.00	$61.00
Purchase #7	$45.27	5.764%	$47.8794	$47.88	$47.90	$47.90
7 purchase totals =	$520.37		$570.3643	$570.38	$570.45	$570.30