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	$76.88	7.479%	$82.6299	$82.63	$82.65	$82.60
Purchase #2	$38.55	11.715%	$43.0661	$43.07	$43.05	$43.10
Purchase #3	$49.52	4.744%	$51.8692	$51.87	$51.85	$51.90
Purchase #4	$122.57	4.272%	$127.8062	$127.81	$127.80	$127.80
Purchase #5	$143.72	10.516%	$158.8336	$158.83	$158.85	$158.80
Purchase #6	$70.47	11.756%	$78.7545	$78.75	$78.75	$78.80
Purchase #7	$83.30	8.690%	$90.5388	$90.54	$90.55	$90.50
7 purchase totals =	$585.01		$633.4983	$633.50	$633.50	$633.50