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	$168.30	8.478%	$182.5685	$182.57	$182.55	$182.60
Purchase #2	$207.30	3.779%	$215.1339	$215.13	$215.15	$215.10
Purchase #3	$18.90	3.395%	$19.5417	$19.54	$19.55	$19.50
Purchase #4	$171.54	11.381%	$191.063	$191.06	$191.05	$191.10
Purchase #5	$162.52	13.378%	$184.2619	$184.26	$184.25	$184.30
Purchase #6	$10.75	3.252%	$11.0996	$11.10	$11.10	$11.10
Purchase #7	$132.59	10.446%	$146.4404	$146.44	$146.45	$146.40
7 purchase totals =	$871.90		$950.1090	$950.10	$950.10	$950.10