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	$115.31	10.309%	$127.1973	$127.20	$127.20	$127.20
Purchase #2	$222.85	3.460%	$230.5606	$230.56	$230.55	$230.60
Purchase #3	$118.65	13.374%	$134.5183	$134.52	$134.50	$134.50
Purchase #4	$250.27	12.280%	$281.0032	$281.00	$281.00	$281.00
Purchase #5	$142.30	7.318%	$152.7135	$152.71	$152.70	$152.70
Purchase #6	$151.50	8.648%	$164.6017	$164.60	$164.60	$164.60
Purchase #7	$166.29	5.484%	$175.4093	$175.41	$175.40	$175.40
7 purchase totals =	$1,167.17		$1,266.0039	$1,266.00	$1,265.95	$1,266.00