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	$52.45	4.498%	$54.8092	$54.81	$54.80	$54.80
Purchase #2	$138.98	13.737%	$158.0717	$158.07	$158.05	$158.10
Purchase #3	$192.64	10.800%	$213.4451	$213.45	$213.45	$213.40
Purchase #4	$239.72	3.276%	$247.5732	$247.57	$247.55	$247.60
Purchase #5	$121.27	12.152%	$136.0067	$136.01	$136.00	$136.00
Purchase #6	$231.57	3.166%	$238.9015	$238.90	$238.90	$238.90
Purchase #7	$219.46	6.470%	$233.6591	$233.66	$233.65	$233.70
7 purchase totals =	$1,196.09		$1,282.4665	$1,282.47	$1,282.40	$1,282.50