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	$74.26	12.431%	$83.4913	$83.49	$83.50	$83.50
Purchase #2	$109.55	11.858%	$122.5404	$122.54	$122.55	$122.50
Purchase #3	$183.56	3.536%	$190.0507	$190.05	$190.05	$190.10
Purchase #4	$173.93	3.533%	$180.0749	$180.07	$180.05	$180.10
Purchase #5	$151.57	11.227%	$168.5868	$168.59	$168.60	$168.60
Purchase #6	$166.27	13.368%	$188.497	$188.50	$188.50	$188.50
Purchase #7	$139.81	4.206%	$145.6904	$145.69	$145.70	$145.70
7 purchase totals =	$998.95		$1,078.9315	$1,078.93	$1,078.95	$1,079.00