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	$117.63	9.346%	$128.6237	$128.62	$128.60	$128.60
Purchase #2	$84.27	7.129%	$90.2776	$90.28	$90.30	$90.30
Purchase #3	$179.97	9.326%	$196.754	$196.75	$196.75	$196.80
Purchase #4	$45.72	7.199%	$49.0114	$49.01	$49.00	$49.00
Purchase #5	$60.59	8.338%	$65.642	$65.64	$65.65	$65.60
Purchase #6	$61.89	5.540%	$65.3187	$65.32	$65.30	$65.30
Purchase #7	$122.76	11.268%	$136.5926	$136.59	$136.60	$136.60
7 purchase totals =	$672.83		$732.2200	$732.21	$732.20	$732.20