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	$133.71	4.766%	$140.0826	$140.08	$140.10	$140.10
Purchase #2	$78.82	5.661%	$83.282	$83.28	$83.30	$83.30
Purchase #3	$193.65	13.498%	$219.7889	$219.79	$219.80	$219.80
Purchase #4	$103.84	7.618%	$111.7505	$111.75	$111.75	$111.80
Purchase #5	$134.76	3.157%	$139.0144	$139.01	$139.00	$139.00
Purchase #6	$184.83	10.130%	$203.5533	$203.55	$203.55	$203.60
Purchase #7	$102.41	12.652%	$115.3669	$115.37	$115.35	$115.40
7 purchase totals =	$932.02		$1,012.8386	$1,012.83	$1,012.85	$1,013.00