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	$112.52	10.673%	$124.5293	$124.53	$124.55	$124.50
Purchase #2	$29.48	6.597%	$31.4248	$31.42	$31.40	$31.40
Purchase #3	$59.78	7.635%	$64.3442	$64.34	$64.35	$64.30
Purchase #4	$233.46	4.553%	$244.0894	$244.09	$244.10	$244.10
Purchase #5	$54.95	12.699%	$61.9281	$61.93	$61.95	$61.90
Purchase #6	$36.98	9.775%	$40.5948	$40.59	$40.60	$40.60
Purchase #7	$126.69	4.276%	$132.1073	$132.11	$132.10	$132.10
7 purchase totals =	$653.86		$699.0179	$699.01	$699.05	$698.90