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	$73.30	10.725%	$81.1614	$81.16	$81.15	$81.20
Purchase #2	$71.58	9.734%	$78.5476	$78.55	$78.55	$78.50
Purchase #3	$127.82	5.330%	$134.6328	$134.63	$134.65	$134.60
Purchase #4	$147.41	4.685%	$154.3162	$154.32	$154.30	$154.30
Purchase #5	$225.89	6.166%	$239.8184	$239.82	$239.80	$239.80
Purchase #6	$230.41	3.470%	$238.4052	$238.41	$238.40	$238.40
Purchase #7	$185.55	3.489%	$192.0238	$192.02	$192.00	$192.00
7 purchase totals =	$1,061.96		$1,118.9054	$1,118.91	$1,118.85	$1,118.80