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	$71.29	6.385%	$75.8419	$75.84	$75.85	$75.80
Purchase #2	$161.49	5.273%	$170.0054	$170.01	$170.00	$170.00
Purchase #3	$150.81	10.373%	$166.4535	$166.45	$166.45	$166.50
Purchase #4	$160.55	3.710%	$166.5064	$166.51	$166.50	$166.50
Purchase #5	$115.87	9.695%	$127.1036	$127.10	$127.10	$127.10
Purchase #6	$146.32	6.583%	$155.9522	$155.95	$155.95	$156.00
Purchase #7	$228.65	9.218%	$249.727	$249.73	$249.75	$249.70
7 purchase totals =	$1,034.98		$1,111.5900	$1,111.59	$1,111.60	$1,111.60