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	$162.25	5.854%	$171.7481	$171.75	$171.75	$171.70
Purchase #2	$148.26	12.725%	$167.1261	$167.13	$167.15	$167.10
Purchase #3	$146.48	3.742%	$151.9613	$151.96	$151.95	$152.00
Purchase #4	$127.46	3.613%	$132.0651	$132.07	$132.05	$132.10
Purchase #5	$158.54	3.763%	$164.5059	$164.51	$164.50	$164.50
Purchase #6	$92.26	13.822%	$105.0122	$105.01	$105.00	$105.00
Purchase #7	$207.81	8.535%	$225.5466	$225.55	$225.55	$225.50
7 purchase totals =	$1,043.06		$1,117.9653	$1,117.98	$1,117.95	$1,117.90