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	$218.37	9.314%	$238.709	$238.71	$238.70	$238.70
Purchase #2	$81.27	4.516%	$84.9402	$84.94	$84.95	$84.90
Purchase #3	$148.26	12.818%	$167.264	$167.26	$167.25	$167.30
Purchase #4	$179.98	9.420%	$196.9341	$196.93	$196.95	$196.90
Purchase #5	$52.60	5.247%	$55.3599	$55.36	$55.35	$55.40
Purchase #6	$144.76	11.444%	$161.3263	$161.33	$161.35	$161.30
Purchase #7	$123.83	12.482%	$139.2865	$139.29	$139.30	$139.30
7 purchase totals =	$949.07		$1,043.8200	$1,043.82	$1,043.85	$1,043.80