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	$203.59	12.672%	$229.3889	$229.39	$229.40	$229.40
Purchase #2	$170.72	8.633%	$185.4583	$185.46	$185.45	$185.50
Purchase #3	$66.90	7.661%	$72.0252	$72.03	$72.05	$72.00
Purchase #4	$47.78	8.649%	$51.9125	$51.91	$51.90	$51.90
Purchase #5	$240.30	6.121%	$255.0088	$255.01	$255.00	$255.00
Purchase #6	$206.36	13.329%	$233.8657	$233.87	$233.85	$233.90
Purchase #7	$111.90	5.239%	$117.7624	$117.76	$117.75	$117.80
7 purchase totals =	$1,047.55		$1,145.4218	$1,145.43	$1,145.40	$1,145.50