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	$144.32	4.199%	$150.38	$150.38	$150.40	$150.40
Purchase #2	$20.72	12.292%	$23.2669	$23.27	$23.25	$23.30
Purchase #3	$196.44	8.602%	$213.3378	$213.34	$213.35	$213.30
Purchase #4	$29.35	8.824%	$31.9398	$31.94	$31.95	$31.90
Purchase #5	$225.98	5.665%	$238.7818	$238.78	$238.80	$238.80
Purchase #6	$229.69	3.713%	$238.2184	$238.22	$238.20	$238.20
Purchase #7	$171.62	11.111%	$190.6887	$190.69	$190.70	$190.70
7 purchase totals =	$1,018.12		$1,086.6134	$1,086.62	$1,086.65	$1,086.60