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	$209.38	12.433%	$235.4122	$235.41	$235.40	$235.40
Purchase #2	$42.28	5.570%	$44.635	$44.64	$44.65	$44.60
Purchase #3	$137.97	4.706%	$144.4629	$144.46	$144.45	$144.50
Purchase #4	$202.97	7.789%	$218.7793	$218.78	$218.80	$218.80
Purchase #5	$176.96	11.167%	$196.7211	$196.72	$196.70	$196.70
Purchase #6	$162.78	13.478%	$184.7195	$184.72	$184.70	$184.70
Purchase #7	$232.43	11.626%	$259.4523	$259.45	$259.45	$259.50
7 purchase totals =	$1,164.77		$1,284.1823	$1,284.18	$1,284.15	$1,284.20