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	$142.26	9.417%	$155.6566	$155.66	$155.65	$155.70
Purchase #2	$111.70	13.745%	$127.0532	$127.05	$127.05	$127.10
Purchase #3	$63.49	12.830%	$71.6358	$71.64	$71.65	$71.60
Purchase #4	$38.40	5.690%	$40.585	$40.59	$40.60	$40.60
Purchase #5	$64.68	9.258%	$70.6681	$70.67	$70.65	$70.70
Purchase #6	$142.32	5.328%	$149.9028	$149.90	$149.90	$149.90
Purchase #7	$83.82	10.790%	$92.8642	$92.86	$92.85	$92.90
7 purchase totals =	$646.67		$708.3657	$708.37	$708.35	$708.50