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	$43.49	9.214%	$47.4972	$47.50	$47.50	$47.50
Purchase #2	$54.51	4.478%	$56.951	$56.95	$56.95	$57.00
Purchase #3	$75.79	4.174%	$78.9535	$78.95	$78.95	$79.00
Purchase #4	$196.91	6.162%	$209.0436	$209.04	$209.05	$209.00
Purchase #5	$136.42	11.144%	$151.6226	$151.62	$151.60	$151.60
Purchase #6	$131.88	9.597%	$144.5365	$144.54	$144.55	$144.50
Purchase #7	$14.50	9.792%	$15.9198	$15.92	$15.90	$15.90
7 purchase totals =	$653.50		$704.5242	$704.52	$704.50	$704.50