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	$105.93	5.327%	$111.5729	$111.57	$111.55	$111.60
Purchase #2	$60.39	4.240%	$62.9505	$62.95	$62.95	$63.00
Purchase #3	$74.65	5.633%	$78.855	$78.86	$78.85	$78.90
Purchase #4	$107.53	8.706%	$116.8916	$116.89	$116.90	$116.90
Purchase #5	$215.93	9.702%	$236.8795	$236.88	$236.90	$236.90
Purchase #6	$224.65	11.277%	$249.9838	$249.98	$250.00	$250.00
Purchase #7	$52.51	5.617%	$55.4595	$55.46	$55.45	$55.50
7 purchase totals =	$841.59		$912.5928	$912.59	$912.60	$912.80