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	$57.43	7.200%	$61.565	$61.57	$61.55	$61.60
Purchase #2	$167.86	9.829%	$184.359	$184.36	$184.35	$184.40
Purchase #3	$100.81	4.260%	$105.1045	$105.10	$105.10	$105.10
Purchase #4	$9.82	8.263%	$10.6314	$10.63	$10.65	$10.60
Purchase #5	$45.78	13.566%	$51.9905	$51.99	$52.00	$52.00
Purchase #6	$86.83	3.207%	$89.6146	$89.61	$89.60	$89.60
Purchase #7	$37.30	9.333%	$40.7812	$40.78	$40.80	$40.80
7 purchase totals =	$505.83		$544.0462	$544.04	$544.05	$544.10