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	$173.85	3.846%	$180.5363	$180.54	$180.55	$180.50
Purchase #2	$90.63	11.802%	$101.3262	$101.33	$101.35	$101.30
Purchase #3	$135.52	4.161%	$141.159	$141.16	$141.15	$141.20
Purchase #4	$185.70	5.866%	$196.5932	$196.59	$196.60	$196.60
Purchase #5	$180.98	6.243%	$192.2786	$192.28	$192.30	$192.30
Purchase #6	$57.64	12.353%	$64.7603	$64.76	$64.75	$64.80
Purchase #7	$200.52	6.773%	$214.1012	$214.10	$214.10	$214.10
7 purchase totals =	$1,024.84		$1,090.7548	$1,090.76	$1,090.80	$1,090.80