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	$243.82	13.301%	$276.2505	$276.25	$276.25	$276.30
Purchase #2	$194.94	12.385%	$219.0833	$219.08	$219.10	$219.10
Purchase #3	$24.52	13.605%	$27.8559	$27.86	$27.85	$27.90
Purchase #4	$167.31	11.652%	$186.805	$186.81	$186.80	$186.80
Purchase #5	$110.43	3.346%	$114.125	$114.13	$114.15	$114.10
Purchase #6	$75.33	10.865%	$83.5146	$83.51	$83.50	$83.50
Purchase #7	$113.33	12.139%	$127.0871	$127.09	$127.10	$127.10
7 purchase totals =	$929.68		$1,034.7214	$1,034.73	$1,034.75	$1,034.80