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	$216.41	12.709%	$243.9135	$243.91	$243.90	$243.90
Purchase #2	$69.91	11.683%	$78.0776	$78.08	$78.10	$78.10
Purchase #3	$113.55	4.730%	$118.9209	$118.92	$118.90	$118.90
Purchase #4	$154.86	7.406%	$166.3289	$166.33	$166.35	$166.30
Purchase #5	$86.62	9.137%	$94.5345	$94.53	$94.55	$94.50
Purchase #6	$238.28	4.602%	$249.2456	$249.25	$249.25	$249.20
Purchase #7	$62.44	9.698%	$68.4954	$68.50	$68.50	$68.50
7 purchase totals =	$942.07		$1,019.5164	$1,019.52	$1,019.55	$1,019.40