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	$177.38	11.757%	$198.2346	$198.23	$198.25	$198.20
Purchase #2	$203.42	12.405%	$228.6543	$228.65	$228.65	$228.70
Purchase #3	$63.39	13.552%	$71.9806	$71.98	$72.00	$72.00
Purchase #4	$115.62	6.598%	$123.2486	$123.25	$123.25	$123.20
Purchase #5	$35.90	6.688%	$38.301	$38.30	$38.30	$38.30
Purchase #6	$119.72	13.650%	$136.0618	$136.06	$136.05	$136.10
Purchase #7	$224.59	10.145%	$247.3747	$247.37	$247.35	$247.40
7 purchase totals =	$940.02		$1,043.8556	$1,043.84	$1,043.85	$1,043.90