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	$42.39	12.450%	$47.6676	$47.67	$47.65	$47.70
Purchase #2	$98.59	12.831%	$111.2401	$111.24	$111.25	$111.20
Purchase #3	$138.90	12.748%	$156.607	$156.61	$156.60	$156.60
Purchase #4	$151.27	11.294%	$168.3544	$168.35	$168.35	$168.40
Purchase #5	$133.32	12.717%	$150.2743	$150.27	$150.25	$150.30
Purchase #6	$108.74	12.423%	$122.2488	$122.25	$122.25	$122.20
Purchase #7	$182.52	5.248%	$192.0986	$192.10	$192.10	$192.10
7 purchase totals =	$855.73		$948.4908	$948.49	$948.45	$948.50