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	$58.80	11.454%	$65.535	$65.54	$65.55	$65.50
Purchase #2	$165.32	8.241%	$178.944	$178.94	$178.95	$178.90
Purchase #3	$187.28	4.784%	$196.2395	$196.24	$196.25	$196.20
Purchase #4	$74.43	9.343%	$81.384	$81.38	$81.40	$81.40
Purchase #5	$168.95	10.140%	$186.0815	$186.08	$186.10	$186.10
Purchase #6	$172.35	4.209%	$179.6042	$179.60	$179.60	$179.60
Purchase #7	$56.54	8.483%	$61.3363	$61.34	$61.35	$61.30
7 purchase totals =	$883.67		$949.1245	$949.12	$949.20	$949.00